Lint the code.

Add support for Python 3.9 and 3.10.

CHANGES.rst

@@ -2,7 +2,7 @@
  Change History
 ================
 
-5.6.1 (unreleased)
+5.7.0 (unreleased)
 ==================
 
 - Fix ``TypeError: can't concat str to bytes`` when running fsoids.py script with Python 3.
@@ -24,6 +24,8 @@
 
 - Fix deprecation warnings occurring on Python 3.10.
 
+- Add support for Python 3.9 and 3.10.
+
 
 5.6.0 (2020-06-11)
 ==================

docs/conf.py

@@ -56,7 +56,7 @@ master_doc = 'index'
 
 # General information about the project.
 project = 'ZODB'
-copyright = '2009-2020, Zope Foundation'
+copyright = '2009-2021, Zope Foundation'
 
 # The version info for the project you're documenting, acts as replacement for
 # |version| and |release|, also used in various other places throughout the

setup.py

@@ -13,7 +13,7 @@
 ##############################################################################
 from setuptools import setup, find_packages
 
-version = '5.6.1.dev0'
+version = '5.7.0.dev0'
 
 classifiers = """\
 Intended Audience :: Developers
@@ -26,6 +26,8 @@ Programming Language :: Python :: 3.5
 Programming Language :: Python :: 3.6
 Programming Language :: Python :: 3.7
 Programming Language :: Python :: 3.8
+Programming Language :: Python :: 3.9
+Programming Language :: Python :: 3.10
 Programming Language :: Python :: Implementation :: CPython
 Programming Language :: Python :: Implementation :: PyPy
 Topic :: Database
@@ -35,10 +37,12 @@ Operating System :: Unix
 Framework :: ZODB
 """
 
+
 def read(path):
     with open(path) as f:
         return f.read()
 
+
 long_description = read("README.rst") + "\n\n" + read("CHANGES.rst")
 
 tests_require = [
@@ -67,6 +71,13 @@ setup(
     tests_require=tests_require,
     extras_require={
         'test': tests_require,
+        'docs': [
+            'Sphinx',
+            'ZODB',
+            'j1m.sphinxautozconfig',
+            'sphinx_rtd_theme',
+            'sphinxcontrib_zopeext',
+        ]
     },
     install_requires=[
         'persistent >= 4.4.0',

src/ZODB/ActivityMonitor.py

@@ -72,7 +72,7 @@ class ActivityMonitor(object):
                 'loads': 0,
                 'stores': 0,
                 'connections': 0,
-                })
+            })
 
         div = res[0]
         div_end = div['end']

src/ZODB/BaseStorage.py

@@ -20,7 +20,6 @@ from __future__ import print_function
 
 import time
 import logging
-import sys
 from struct import pack as _structpack, unpack as _structunpack
 
 import zope.interface
@@ -35,6 +34,7 @@ from ._compat import py2_hasattr
 
 log = logging.getLogger("ZODB.BaseStorage")
 
+
 class BaseStorage(UndoLogCompatible):
     """Base class that supports storage implementations.
 
@@ -74,12 +74,12 @@ class BaseStorage(UndoLogCompatible):
     perhaps other things.  It is always held when load() is called, so
     presumably the load() implementation should also acquire the lock.
     """
-    _transaction=None # Transaction that is being committed
-    _tstatus=' '      # Transaction status, used for copying data
+    _transaction = None  # Transaction that is being committed
+    _tstatus = ' '      # Transaction status, used for copying data
     _is_read_only = False
 
     def __init__(self, name, base=None):
-        self.__name__= name
+        self.__name__ = name
         log.debug("create storage %s", self.__name__)
 
         # Allocate locks:
@@ -93,7 +93,7 @@ class BaseStorage(UndoLogCompatible):
         self._commit_lock_release = self._commit_lock.release
 
         t = time.time()
-        t = self._ts = TimeStamp(*(time.gmtime(t)[:5] + (t%60,)))
+        t = self._ts = TimeStamp(*(time.gmtime(t)[:5] + (t % 60,)))
         self._tid = t.raw()
 
         # ._oid is the highest oid in use (0 is always in use -- it's
@@ -122,7 +122,7 @@ class BaseStorage(UndoLogCompatible):
         return self.__name__
 
     def getSize(self):
-        return len(self)*300 # WAG!
+        return len(self)*300  # WAG!
 
     def history(self, oid, version, length=1, filter=None):
         return ()
@@ -151,7 +151,7 @@ class BaseStorage(UndoLogCompatible):
                 self._oid = possible_new_max_oid
 
     def registerDB(self, db):
-        pass # we don't care
+        pass  # we don't care
 
     def isReadOnly(self):
         return self._is_read_only
@@ -279,6 +279,7 @@ class BaseStorage(UndoLogCompatible):
         """
         copy(other, self, verbose)
 
+
 def copy(source, dest, verbose=0):
     """Copy transactions from a source to a destination storage
 
@@ -287,7 +288,7 @@ def copy(source, dest, verbose=0):
     """
     _ts = None
     ok = 1
-    preindex = {};
+    preindex = {}
     preget = preindex.get
     # restore() is a new storage API method which has an identical
     # signature to store() except that it does not return anything.
@@ -310,7 +311,8 @@ def copy(source, dest, verbose=0):
         else:
             t = TimeStamp(tid)
             if t <= _ts:
-                if ok: print(('Time stamps out of order %s, %s' % (_ts, t)))
+                if ok:
+                    print(('Time stamps out of order %s, %s' % (_ts, t)))
                 ok = 0
                 _ts = t.laterThan(_ts)
                 tid = _ts.raw()
@@ -351,23 +353,24 @@ def checkCurrentSerialInTransaction(self, oid, serial, transaction):
         raise POSException.ReadConflictError(
             oid=oid, serials=(committed_tid, serial))
 
+
 BaseStorage.checkCurrentSerialInTransaction = checkCurrentSerialInTransaction
 
+
 @zope.interface.implementer(ZODB.interfaces.IStorageTransactionInformation)
 class TransactionRecord(TransactionMetaData):
     """Abstract base class for iterator protocol"""
 
-
     def __init__(self, tid, status, user, description, extension):
         self.tid = tid
         self.status = status
         TransactionMetaData.__init__(self, user, description, extension)
 
+
 @zope.interface.implementer(ZODB.interfaces.IStorageRecordInformation)
 class DataRecord(object):
     """Abstract base class for iterator protocol"""
 
-
     version = ''
 
     def __init__(self, oid, tid, data, prev):

src/ZODB/ConflictResolution.py

@@ -29,9 +29,11 @@ from pickle import PicklingError
 
 logger = logging.getLogger('ZODB.ConflictResolution')
 
+
 class BadClassName(Exception):
     pass
 
+
 class BadClass(object):
 
     def __init__(self, *args):
@@ -40,8 +42,11 @@ class BadClass(object):
     def __reduce__(self):
         raise BadClassName(*self.args)
 
+
 _class_cache = {}
 _class_cache_get = _class_cache.get
+
+
 def find_global(*args):
     cls = _class_cache_get(args, 0)
     if cls == 0:
@@ -60,23 +65,24 @@ def find_global(*args):
     if cls == 1:
         # Not importable
         if (isinstance(args, tuple) and len(args) == 2 and
-            isinstance(args[0], six.string_types) and
-            isinstance(args[1], six.string_types)
-            ):
+                isinstance(args[0], six.string_types) and
+                isinstance(args[1], six.string_types)):
             return BadClass(*args)
         else:
             raise BadClassName(*args)
     return cls
 
+
 def state(self, oid, serial, prfactory, p=''):
     p = p or self.loadSerial(oid, serial)
     p = self._crs_untransform_record_data(p)
     file = BytesIO(p)
     unpickler = PersistentUnpickler(
         find_global, prfactory.persistent_load, file)
-    unpickler.load() # skip the class tuple
+    unpickler.load()  # skip the class tuple
     return unpickler.load()
 
+
 class IPersistentReference(zope.interface.Interface):
     '''public contract for references to persistent objects from an object
     with conflicts.'''
@@ -114,10 +120,10 @@ class IPersistentReference(zope.interface.Interface):
         have two references to the same object that are spelled with different
         data (for instance, one with a class and one without).'''
 
+
 @zope.interface.implementer(IPersistentReference)
 class PersistentReference(object):
 
-
     weak = False
     oid = database_name = klass = None
 
@@ -134,7 +140,7 @@ class PersistentReference(object):
                 self.data = self.oid, klass.args
         elif isinstance(data, (bytes, str)):
             self.oid = data
-        else: # a list
+        else:  # a list
             reference_type = data[0]
             # 'm' = multi_persistent: (database_name, oid, klass)
             # 'n' = multi_oid: (database_name, oid)
@@ -165,11 +171,11 @@ class PersistentReference(object):
 
     def __cmp__(self, other):
         if self is other or (
-            isinstance(other, PersistentReference) and
-            self.oid == other.oid and
-            self.database_name == other.database_name and
-            not self.weak and
-            not other.weak):
+                isinstance(other, PersistentReference) and
+                self.oid == other.oid and
+                self.database_name == other.database_name and
+                not self.weak and
+                not other.weak):
             return 0
         else:
             raise ValueError(
@@ -211,6 +217,7 @@ class PersistentReference(object):
         elif isinstance(data, list) and data[0] == 'm':
             return data[1][2]
 
+
 class PersistentReferenceFactory(object):
 
     data = None
@@ -218,7 +225,8 @@ class PersistentReferenceFactory(object):
     def persistent_load(self, ref):
         if self.data is None:
             self.data = {}
-        key = tuple(ref) # lists are not hashable; formats are different enough
+        # lists are not hashable; formats are different enough
+        key = tuple(ref)
         # even after eliminating list/tuple distinction
         r = self.data.get(key, None)
         if r is None:
@@ -227,12 +235,16 @@ class PersistentReferenceFactory(object):
 
         return r
 
+
 def persistent_id(object):
     if getattr(object, '__class__', 0) is not PersistentReference:
         return None
     return object.data
 
+
 _unresolvable = {}
+
+
 def tryToResolveConflict(self, oid, committedSerial, oldSerial, newpickle,
                          committedData=b''):
     # class_tuple, old, committed, newstate = ('',''), 0, 0, 0
@@ -264,13 +276,12 @@ def tryToResolveConflict(self, oid, committedSerial, oldSerial, newpickle,
             _unresolvable[klass] = 1
             raise ConflictError
 
-
         oldData = self.loadSerial(oid, oldSerial)
         if not committedData:
-            committedData  = self.loadSerial(oid, committedSerial)
+            committedData = self.loadSerial(oid, committedSerial)
 
         newstate = unpickler.load()
-        old       = state(self, oid, oldSerial, prfactory, oldData)
+        old = state(self, oid, oldSerial, prfactory, oldData)
         committed = state(self, oid, committedSerial, prfactory, committedData)
 
         resolved = resolve(old, committed, newstate)
@@ -284,7 +295,7 @@ def tryToResolveConflict(self, oid, committedSerial, oldSerial, newpickle,
         logger.debug(
             "Conflict resolution on %s failed with %s: %s",
             klass, e.__class__.__name__, str(e))
-    except:
+    except:  # noqa: E722 do not use bare 'except'
         # If anything else went wrong, catch it here and avoid passing an
         # arbitrary exception back to the client.  The error here will mask
         # the original ConflictError.  A client can recover from a
@@ -296,6 +307,7 @@ def tryToResolveConflict(self, oid, committedSerial, oldSerial, newpickle,
     raise ConflictError(oid=oid, serials=(committedSerial, oldSerial),
                         data=newpickle)
 
+
 class ConflictResolvingStorage(object):
     "Mix-in class that provides conflict resolution handling for storages"
 

src/ZODB/DB.py

@@ -41,6 +41,7 @@ from ZODB import valuedoc
 
 logger = logging.getLogger('ZODB.DB')
 
+
 class AbstractConnectionPool(object):
     """Manage a pool of connections.
 
@@ -111,7 +112,7 @@ class AbstractConnectionPool(object):
 
 class ConnectionPool(AbstractConnectionPool):
 
-    def __init__(self, size, timeout=1<<31):
+    def __init__(self, size, timeout=1 << 31):
         super(ConnectionPool, self).__init__(size, timeout)
 
         # A stack of connections available to hand out.  This is a subset
@@ -127,9 +128,8 @@ class ConnectionPool(AbstractConnectionPool):
     def _append(self, c):
         available = self.available
         cactive = c._cache.cache_non_ghost_count
-        if (available and
-            (available[-1][1]._cache.cache_non_ghost_count > cactive)
-            ):
+        if (available
+                and (available[-1][1]._cache.cache_non_ghost_count > cactive)):
             i = len(available) - 1
             while (i and
                    (available[i-1][1]._cache.cache_non_ghost_count > cactive)
@@ -185,7 +185,7 @@ class ConnectionPool(AbstractConnectionPool):
             (len(available) > target)
             or
             (available and available[0][0] < threshhold)
-            ):
+        ):
             t, c = available.pop(0)
             assert not c.opened
             self.all.remove(c)
@@ -244,7 +244,7 @@ class KeyedConnectionPool(AbstractConnectionPool):
 
     # see the comments in ConnectionPool for method descriptions.
 
-    def __init__(self, size, timeout=1<<31):
+    def __init__(self, size, timeout=1 << 31):
         super(KeyedConnectionPool, self).__init__(size, timeout)
         self.pools = {}
 
@@ -303,6 +303,7 @@ def toTimeStamp(dt):
     args = utc_struct[:5]+(utc_struct[5] + dt.microsecond/1000000.0,)
     return TimeStamp(*args)
 
+
 def getTID(at, before):
     if at is not None:
         if before is not None:
@@ -319,6 +320,7 @@ def getTID(at, before):
             before = TimeStamp(before).raw()
     return before
 
+
 @implementer(IDatabase)
 class DB(object):
     """The Object Database
@@ -348,7 +350,7 @@ class DB(object):
     def __init__(self,
                  storage,
                  pool_size=7,
-                 pool_timeout=1<<31,
+                 pool_timeout=1 << 31,
                  cache_size=400,
                  cache_size_bytes=0,
                  historical_pool_size=3,
@@ -358,7 +360,7 @@ class DB(object):
                  database_name='unnamed',
                  databases=None,
                  xrefs=True,
-                 large_record_size=1<<24,
+                 large_record_size=1 << 24,
                  **storage_args):
         """Create an object database.
 
@@ -425,10 +427,10 @@ class DB(object):
 
         # Setup storage
         if isinstance(storage, six.string_types):
-            from ZODB import FileStorage
+            from ZODB import FileStorage  # noqa: F401 import unused
             storage = ZODB.FileStorage.FileStorage(storage, **storage_args)
         elif storage is None:
-            from ZODB import MappingStorage
+            from ZODB import MappingStorage  # noqa: F401 import unused
             storage = ZODB.MappingStorage.MappingStorage(**storage_args)
         else:
             assert not storage_args
@@ -507,6 +509,7 @@ class DB(object):
         """
 
         detail = {}
+
         def f(con, detail=detail):
             for oid, ob in con._cache.items():
                 module = getattr(ob.__class__, '__module__', '')
@@ -570,17 +573,18 @@ class DB(object):
                     'rc': (rc(ob) - 3 - (ob._p_changed is not None)
                            if rc else False),
                     'state': ob._p_changed,
-                    #'references': con.references(oid),
-                    })
+                    # 'references': con.references(oid),
+                })
 
         self._connectionMap(f)
         return detail
 
-    def cacheFullSweep(self): # XXX this is the same as cacheMinimize
+    def cacheFullSweep(self):  # XXX this is the same as cacheMinimize
         self._connectionMap(lambda c: c._cache.full_sweep())
 
     def cacheLastGCTime(self):
         m = [0]
+
         def f(con, m=m):
             t = con._cache.cache_last_gc_time
             if t > m[0]:
@@ -598,6 +602,7 @@ class DB(object):
         """Return the total count of non-ghost objects in all object caches
         """
         m = [0]
+
         def f(con, m=m):
             m[0] += con._cache.cache_non_ghost_count
 
@@ -608,6 +613,7 @@ class DB(object):
         """Return non-ghost counts sizes for all connections.
         """
         m = []
+
         def f(con, m=m):
             m.append({'connection': repr(con),
                       'ngsize': con._cache.cache_non_ghost_count,
@@ -731,7 +737,7 @@ class DB(object):
         before = getTID(at, before)
         if (before is not None and
             before > self.lastTransaction() and
-            before > getTID(self.lastTransaction(), None)):
+                before > getTID(self.lastTransaction(), None)):
             raise ValueError(
                 'cannot open an historical connection in the future.')
 
@@ -773,7 +779,6 @@ class DB(object):
             self.pool.availableGC()
             self.historical_pool.availableGC()
 
-
         result.open(transaction_manager)
         return result
 
@@ -808,7 +813,7 @@ class DB(object):
                     t-o)),
                 'info': d,
                 'before': c.before,
-                })
+            })
 
         self._connectionMap(get_info)
         return result
@@ -836,7 +841,7 @@ class DB(object):
         t -= days * 86400
         try:
             self.storage.pack(t, self.references)
-        except:
+        except:  # noqa: E722 do not use bare 'except'
             logger.exception("packing")
             raise
 
@@ -994,7 +999,7 @@ class DB(object):
         Kept for backwards compatibility only. New oids should be
         allocated in a transaction using an open Connection.
         """
-        return self.storage.new_oid() # pragma: no cover
+        return self.storage.new_oid()  # pragma: no cover
 
     def open_then_close_db_when_connection_closes(self):
         """Create and return a connection.
@@ -1029,9 +1034,11 @@ class ContextManager(object):
             self.tm.abort()
         self.conn.close()
 
+
 resource_counter_lock = utils.Lock()
 resource_counter = 0
 
+
 class TransactionalUndo(object):
 
     def __init__(self, db, tids):
@@ -1064,9 +1071,10 @@ class TransactionalUndo(object):
         # a new storage instance, and so we must close it to be sure
         # to reclaim resources in a timely manner.
         #
-        # Once the tpc_begin method has been called, the transaction manager will
-        # guarantee to call either `tpc_finish` or `tpc_abort`, so those are the only
-        # methods we need to be concerned about calling close() from.
+        # Once the tpc_begin method has been called, the transaction manager
+        # will guarantee to call either `tpc_finish` or `tpc_abort`, so those
+        # are the only methods we need to be concerned about calling close()
+        # from.
         db_mvcc_storage = self._db._mvcc_storage
         self._storage = getattr(
             db_mvcc_storage,
@@ -1117,7 +1125,10 @@ def connection(*args, **kw):
     """
     return DB(*args, **kw).open_then_close_db_when_connection_closes()
 
+
 _transaction_meta_data_text_variables = 'user_name', 'description'
+
+
 def _text_transaction_info(info):
     for d in info:
         for name in _transaction_meta_data_text_variables:

src/ZODB/DemoStorage.py

@@ -35,10 +35,11 @@ import zope.interface
 from .ConflictResolution import ConflictResolvingStorage
 from .utils import load_current, maxtid
 
+
 @zope.interface.implementer(
-        ZODB.interfaces.IStorage,
-        ZODB.interfaces.IStorageIteration,
-        )
+    ZODB.interfaces.IStorage,
+    ZODB.interfaces.IStorageIteration,
+)
 class DemoStorage(ConflictResolvingStorage):
     """A storage that stores changes against a read-only base database
 
@@ -99,7 +100,6 @@ class DemoStorage(ConflictResolvingStorage):
         self.base = base
         self.close_base_on_close = close_base_on_close
 
-
         if changes is None:
             self._temporary_changes = True
             changes = ZODB.MappingStorage.MappingStorage()
@@ -128,16 +128,15 @@ class DemoStorage(ConflictResolvingStorage):
 
         self._copy_methods_from_changes(changes)
 
-        self._next_oid = random.randint(1, 1<<62)
+        self._next_oid = random.randint(1, 1 << 62)
 
     def _blobify(self):
         if (self._temporary_changes and
-            isinstance(self.changes, ZODB.MappingStorage.MappingStorage)
-            ):
+                isinstance(self.changes, ZODB.MappingStorage.MappingStorage)):
             blob_dir = tempfile.mkdtemp('.demoblobs')
             _temporary_blobdirs[
                 weakref.ref(self, cleanup_temporary_blobdir)
-                ] = blob_dir
+            ] = blob_dir
             self.changes = ZODB.blob.BlobStorage(blob_dir, self.changes)
             self._copy_methods_from_changes(self.changes)
             return True
@@ -147,6 +146,7 @@ class DemoStorage(ConflictResolvingStorage):
         self.changes.cleanup()
 
     __opened = True
+
     def opened(self):
         return self.__opened
 
@@ -162,7 +162,7 @@ class DemoStorage(ConflictResolvingStorage):
             '_lock',
             'getSize', 'isReadOnly',
             'sortKey', 'tpc_transaction',
-            ):
+        ):
             setattr(self, meth, getattr(changes, meth))
 
         supportsUndo = getattr(changes, 'supportsUndo', None)
@@ -253,7 +253,7 @@ class DemoStorage(ConflictResolvingStorage):
                         t = self.changes.loadBefore(oid, end_tid)
                     result = result[:2] + (
                         end_tid if end_tid != maxtid else None,
-                        )
+                    )
 
         return result
 
@@ -296,7 +296,7 @@ class DemoStorage(ConflictResolvingStorage):
     def new_oid(self):
         with self._lock:
             while 1:
-                oid = ZODB.utils.p64(self._next_oid )
+                oid = ZODB.utils.p64(self._next_oid)
                 if oid not in self._issued_oids:
                     try:
                         load_current(self.changes, oid)
@@ -308,7 +308,7 @@ class DemoStorage(ConflictResolvingStorage):
                             self._issued_oids.add(oid)
                             return oid
 
-                self._next_oid = random.randint(1, 1<<62)
+                self._next_oid = random.randint(1, 1 << 62)
 
     def pack(self, t, referencesf, gc=None):
         if gc is None:
@@ -325,7 +325,7 @@ class DemoStorage(ConflictResolvingStorage):
             self.changes.pack(t, referencesf, gc=False)
         except TypeError as v:
             if 'gc' in str(v):
-                pass # The gc arg isn't supported. Don't pack
+                pass  # The gc arg isn't supported. Don't pack
             raise
 
     def pop(self):
@@ -344,7 +344,7 @@ class DemoStorage(ConflictResolvingStorage):
                               close_base_on_close=False)
 
     def store(self, oid, serial, data, version, transaction):
-        assert version=='', "versions aren't supported"
+        assert version == '', "versions aren't supported"
         if transaction is not self._transaction:
             raise ZODB.POSException.StorageTransactionError(self, transaction)
 
@@ -367,7 +367,7 @@ class DemoStorage(ConflictResolvingStorage):
 
     def storeBlob(self, oid, oldserial, data, blobfilename, version,
                   transaction):
-        assert version=='', "versions aren't supported"
+        assert version == '', "versions aren't supported"
         if transaction is not self._transaction:
             raise ZODB.POSException.StorageTransactionError(self, transaction)
 
@@ -425,7 +425,7 @@ class DemoStorage(ConflictResolvingStorage):
                 "Unexpected resolved conflicts")
         return self._resolved
 
-    def tpc_finish(self, transaction, func = lambda tid: None):
+    def tpc_finish(self, transaction, func=lambda tid: None):
         with self._lock:
             if (transaction is not self._transaction):
                 raise ZODB.POSException.StorageTransactionError(
@@ -437,11 +437,14 @@ class DemoStorage(ConflictResolvingStorage):
             self._commit_lock.release()
         return tid
 
+
 _temporary_blobdirs = {}
+
+
 def cleanup_temporary_blobdir(
     ref,
-    _temporary_blobdirs=_temporary_blobdirs, # Make sure it stays around
-    ):
+    _temporary_blobdirs=_temporary_blobdirs,  # Make sure it stays around
+):
     blob_dir = _temporary_blobdirs.pop(ref, None)
     if blob_dir and os.path.exists(blob_dir):
         ZODB.blob.remove_committed_dir(blob_dir)

src/ZODB/ExportImport.py

@@ -29,17 +29,17 @@ from ZODB._compat import PersistentPickler, Unpickler, BytesIO, _protocol
 
 logger = logging.getLogger('ZODB.ExportImport')
 
+
 class ExportImport(object):
 
     def exportFile(self, oid, f=None, bufsize=64 * 1024):
         if f is None:
             f = TemporaryFile(prefix="EXP")
         elif isinstance(f, six.string_types):
-            f = open(f,'w+b')
+            f = open(f, 'w+b')
         f.write(b'ZEXP')
         oids = [oid]
         done_oids = {}
-        done = done_oids.__contains__
         load = self._storage.load
         supports_blobs = IBlobStorage.providedBy(self._storage)
         while oids:
@@ -49,7 +49,7 @@ class ExportImport(object):
             done_oids[oid] = True
             try:
                 p, serial = load(oid)
-            except:
+            except:  # noqa: E722 do not use bare 'except'
                 logger.debug("broken reference for oid %s", repr(oid),
                              exc_info=True)
             else:
@@ -58,7 +58,7 @@ class ExportImport(object):
 
                 if supports_blobs:
                     if not isinstance(self._reader.getGhost(p), Blob):
-                        continue # not a blob
+                        continue  # not a blob
 
                     blobfilename = self._storage.loadBlob(oid, serial)
                     f.write(blob_begin_marker)
@@ -159,8 +159,7 @@ class ExportImport(object):
                 return_oid_list.append(oid)
 
             if (b'blob' in data and
-                isinstance(self._reader.getGhost(data), Blob)
-                ):
+                    isinstance(self._reader.getGhost(data), Blob)):
                 # Blob support
 
                 # Make sure we have a (redundant, overly) blob marker.
@@ -198,11 +197,14 @@ class ExportImport(object):
 export_end_marker = b'\377'*16
 blob_begin_marker = b'\000BLOBSTART'
 
+
 class Ghost(object):
     __slots__ = ("oid",)
+
     def __init__(self, oid):
         self.oid = oid
 
+
 def persistent_id(obj):
     if isinstance(obj, Ghost):
         return obj.oid

src/ZODB/FileStorage/format.py

@@ -90,9 +90,11 @@ from ZODB.POSException import POSKeyError
 from ZODB.utils import u64, oid_repr, as_bytes
 from ZODB._compat import PY3
 
+
 class CorruptedError(Exception):
     pass
 
+
 class CorruptedDataError(CorruptedError):
 
     def __init__(self, oid=None, buf=None, pos=None):
@@ -110,6 +112,7 @@ class CorruptedDataError(CorruptedError):
             msg += " at %d" % self.pos
         return msg
 
+
 # the struct formats for the headers
 TRANS_HDR = ">8sQcHHH"
 DATA_HDR = ">8s8sQQHQ"
@@ -121,6 +124,7 @@ assert struct.calcsize(DATA_HDR) == DATA_HDR_LEN
 
 logger = logging.getLogger('ZODB.FileStorage.format')
 
+
 class FileStorageFormatter(object):
     """Mixin class that can read and write the low-level format."""
 
@@ -211,7 +215,7 @@ class FileStorageFormatter(object):
         self.ltid = th.tid
         if th.status == "c":
             self.fail(pos, "transaction with checkpoint flag set")
-        if not th.status in " pu": # recognize " ", "p", and "u" as valid
+        if th.status not in " pu":  # recognize " ", "p", and "u" as valid
             self.fail(pos, "invalid transaction status: %r", th.status)
         if th.tlen < th.headerlen():
             self.fail(pos, "invalid transaction header: "
@@ -232,9 +236,11 @@ class FileStorageFormatter(object):
             if dh.plen:
                 self.fail(pos, "data record has back pointer and data")
 
+
 def DataHeaderFromString(s):
     return DataHeader(*struct.unpack(DATA_HDR, s))
 
+
 class DataHeader(object):
     """Header for a data record."""
 
@@ -250,7 +256,7 @@ class DataHeader(object):
         self.prev = prev
         self.tloc = tloc
         self.plen = plen
-        self.back = 0 # default
+        self.back = 0  # default
 
     def asString(self):
         return struct.pack(DATA_HDR, self.oid, self.tid, self.prev,
@@ -259,12 +265,14 @@ class DataHeader(object):
     def recordlen(self):
         return DATA_HDR_LEN + (self.plen or 8)
 
+
 def TxnHeaderFromString(s):
     res = TxnHeader(*struct.unpack(TRANS_HDR, s))
     if PY3:
         res.status = res.status.decode('ascii')
     return res
 
+
 class TxnHeader(object):
     """Header for a transaction record."""
 

src/ZODB/FileStorage/fsdump.py

@@ -20,19 +20,20 @@ from ZODB.FileStorage.format import DATA_HDR, DATA_HDR_LEN
 from ZODB.TimeStamp import TimeStamp
 from ZODB.utils import u64, get_pickle_metadata
 
+
 def fsdump(path, file=None, with_offset=1):
     iter = FileIterator(path)
     for i, trans in enumerate(iter):
         size = trans._tend - trans._tpos
         if with_offset:
             print(("Trans #%05d tid=%016x size=%d time=%s offset=%d" %
-                  (i, u64(trans.tid), size,
-                   TimeStamp(trans.tid), trans._pos)), file=file)
+                   (i, u64(trans.tid), size,
+                    TimeStamp(trans.tid), trans._pos)), file=file)
         else:
             print(("Trans #%05d tid=%016x size=%d time=%s" %
-                  (i, u64(trans.tid), size, TimeStamp(trans.tid))), file=file)
+                   (i, u64(trans.tid), size, TimeStamp(trans.tid))), file=file)
         print(("    status=%r user=%r description=%r" %
-              (trans.status, trans.user, trans.description)), file=file)
+               (trans.status, trans.user, trans.description)), file=file)
 
         for j, rec in enumerate(trans):
             if rec.data is None:
@@ -51,13 +52,15 @@ def fsdump(path, file=None, with_offset=1):
                 bp = ""
 
             print(("  data #%05d oid=%016x%s class=%s%s" %
-                  (j, u64(rec.oid), size, fullclass, bp)), file=file)
+                   (j, u64(rec.oid), size, fullclass, bp)), file=file)
     iter.close()
 
+
 def fmt(p64):
     # Return a nicely formatted string for a packaged 64-bit value
     return "%016x" % u64(p64)
 
+
 class Dumper(object):
     """A very verbose dumper for debuggin FileStorage problems."""
 
@@ -87,13 +90,13 @@ class Dumper(object):
         print("transaction id: %s" % fmt(tid), file=self.dest)
         print("trec len: %d" % tlen, file=self.dest)
         print("status: %r" % status, file=self.dest)
-        user = descr = extra = ""
+        user = descr = ""
         if ul:
             user = self.file.read(ul)
         if dl:
             descr = self.file.read(dl)
         if el:
-            extra = self.file.read(el)
+            self.file.read(el)
         print("user: %r" % user, file=self.dest)
         print("description: %r" % descr, file=self.dest)
         print("len(extra): %d" % el, file=self.dest)
@@ -121,6 +124,7 @@ class Dumper(object):
             sbp = self.file.read(8)
             print("backpointer: %d" % u64(sbp), file=self.dest)
 
+
 def main():
     import sys
     fsdump(sys.argv[1])

src/ZODB/FileStorage/fsoids.py

@@ -18,10 +18,14 @@ from ZODB.serialize import get_refs
 from ZODB.TimeStamp import TimeStamp
 
 # Extract module.class string from pickle.
+
+
 def get_class(pickle):
     return "%s.%s" % get_pickle_metadata(pickle)
 
 # Shorten a string for display.
+
+
 def shorten(s, size=50):
     if len(s) <= size:
         return s
@@ -35,6 +39,7 @@ def shorten(s, size=50):
         sep = " ... "
     return s[:nleading] + sep + s[-ntrailing:]
 
+
 class Tracer(object):
     """Trace all occurrences of a set of oids in a FileStorage.
 
@@ -84,7 +89,7 @@ class Tracer(object):
             self.oids[oid] = 0  # 0 revisions seen so far
 
     def _msg(self, oid, tid, *args):
-        self.msgs.append( (oid, tid, ' '.join(map(str, args))) )
+        self.msgs.append((oid, tid, ' '.join(map(str, args))))
         self._produced_msg = True
 
     def report(self):
@@ -98,9 +103,9 @@ class Tracer(object):
         NOT_SEEN = "this oid was not defined (no data record for it found)"
         for oid in oids:
             if oid not in oid2name:
-                msgs.append( (oid, None, NOT_SEEN) )
+                msgs.append((oid, None, NOT_SEEN))
 
-        msgs.sort() # oids are primary key, tids secondary
+        msgs.sort()  # oids are primary key, tids secondary
         current_oid = current_tid = None
         for oid, tid, msg in msgs:
             if oid != current_oid:

src/ZODB/FileStorage/fspack.py

@@ -36,9 +36,11 @@ import ZODB.POSException
 
 logger = logging.getLogger(__name__)
 
+
 class PackError(ZODB.POSException.POSError):
     pass
 
+
 class PackCopier(FileStorageFormatter):
 
     def __init__(self, f, index, tindex):
@@ -54,7 +56,7 @@ class PackCopier(FileStorageFormatter):
             self._file.seek(pos - 8)
             pos = pos - u64(self._file.read(8)) - 8
             self._file.seek(pos)
-            h = self._file.read(TRANS_HDR_LEN) # XXX bytes
+            h = self._file.read(TRANS_HDR_LEN)  # XXX bytes
             _tid = h[:8]
             if _tid == tid:
                 return pos
@@ -144,6 +146,7 @@ class PackCopier(FileStorageFormatter):
         finally:
             self._file.seek(pos)
 
+
 class GC(FileStorageFormatter):
 
     def __init__(self, file, eof, packtime, gc, referencesf):
@@ -330,6 +333,7 @@ class GC(FileStorageFormatter):
         else:
             return []
 
+
 class FileStoragePacker(FileStorageFormatter):
 
     # path is the storage file path.
@@ -409,15 +413,15 @@ class FileStoragePacker(FileStorageFormatter):
             # try our best, but don't fail
             try:
                 self._tfile.close()
-            except:
+            except:  # noqa: E722 do not use bare 'except'
                 pass
             try:
                 self._file.close()
-            except:
+            except:  # noqa: E722 do not use bare 'except'
                 pass
             try:
                 os.remove(self._name + ".pack")
-            except:
+            except:  # noqa: E722 do not use bare 'except'
                 pass
             if self.blob_removed is not None:
                 self.blob_removed.close()
@@ -459,8 +463,8 @@ class FileStoragePacker(FileStorageFormatter):
                 # argument, and then on every platform except native
                 # Windows it was observed that we could read stale
                 # data from the tail end of the file.
-                self._file.close() # else self.gc keeps the original
-                                   # alive & open
+                self._file.close()  # else self.gc keeps the original
+                # alive & open
                 self._file = open(self._path, "rb", 0)
                 self._file.seek(0, 2)
                 self.file_end = self._file.tell()
@@ -483,13 +487,12 @@ class FileStoragePacker(FileStorageFormatter):
             if self.locked:
                 self._commit_lock.release()
             raise  # don't succeed silently
-        except:
+        except:  # noqa: E722 do not use bare 'except'
             if self.locked:
                 self._commit_lock.release()
             raise
 
     def copyToPacktime(self):
-        offset = 0  # the amount of space freed by packing
         pos = self._metadata_size
         new_pos = pos
 
@@ -506,7 +509,6 @@ class FileStoragePacker(FileStorageFormatter):
                 self._tfile.seek(new_pos - 8)
                 self._tfile.write(p64(tlen))
 
-
             tlen = self._read_num(pos)
             if tlen != th.tlen:
                 self.fail(pos, "redundant transaction length does not "
@@ -546,8 +548,8 @@ class FileStoragePacker(FileStorageFormatter):
                         # record. There's a bug in ZEO blob support that causes
                         # duplicate data records.
                         rpos = self.gc.reachable.get(h.oid)
-                        is_dup = (rpos
-                                  and self._read_data_header(rpos).tid == h.tid)
+                        is_dup = (
+                            rpos and self._read_data_header(rpos).tid == h.tid)
                         if not is_dup:
                             if h.oid not in self.gc.reachable:
                                 self.blob_removed.write(
@@ -569,7 +571,6 @@ class FileStoragePacker(FileStorageFormatter):
                 s = th.asString()
                 new_tpos = self._tfile.tell()
                 self._tfile.write(s)
-                new_pos = new_tpos + len(s)
                 copy = 1
 
             if h.plen:
@@ -578,7 +579,6 @@ class FileStoragePacker(FileStorageFormatter):
                 data = self.fetchDataViaBackpointer(h.oid, h.back)
 
             self.writePackedDataRecord(h, data, new_tpos)
-            new_pos = self._tfile.tell()
 
         return new_tpos, pos
 

src/ZODB/FileStorage/interfaces.py

@@ -13,6 +13,7 @@
 ##############################################################################
 import zope.interface
 
+
 class IFileStoragePacker(zope.interface.Interface):
 
     def __call__(storage, referencesf, stop, gc):
@@ -58,20 +59,21 @@ class IFileStoragePacker(zope.interface.Interface):
           corresponding to the file records.
         """
 
+
 class IFileStorage(zope.interface.Interface):
 
     packer = zope.interface.Attribute(
         "The IFileStoragePacker to be used for packing."
-        )
+    )
 
     _file = zope.interface.Attribute(
         "The file object used to access the underlying data."
-        )
+    )
 
     _lock = zope.interface.Attribute(
         "The storage lock."
-        )
+    )
 
     _commit_lock = zope.interface.Attribute(
         "The storage commit lock."
-        )
+    )

src/ZODB/FileStorage/tests.py

@@ -29,10 +29,11 @@ checker = renormalizing.RENormalizing([
     # Python 3 adds module name to exceptions.
     (re.compile("ZODB.POSException.POSKeyError"), r"POSKeyError"),
     (re.compile("ZODB.FileStorage.FileStorage.FileStorageQuotaError"),
-                "FileStorageQuotaError"),
+     "FileStorageQuotaError"),
     (re.compile('data.fs:[0-9]+'), 'data.fs:<OFFSET>'),
 ])
 
+
 def pack_keep_old():
     """Should a copy of the database be kept?
 
@@ -106,6 +107,7 @@ directory for blobs is kept.)
     >>> db.close()
     """
 
+
 def pack_with_repeated_blob_records():
     """
     There is a bug in ZEO that causes duplicate bloc database records
@@ -144,6 +146,7 @@ def pack_with_repeated_blob_records():
     >>> db.close()
     """
 
+
 def _save_index():
     """
 
@@ -187,6 +190,7 @@ cleanup
 
     """
 
+
 def pack_disk_full_copyToPacktime():
     """Recover from a disk full situation by removing the `.pack` file
 
@@ -239,6 +243,7 @@ check the data we added
     >>> db.close()
     """
 
+
 def pack_disk_full_copyRest():
     """Recover from a disk full situation by removing the `.pack` file
 
@@ -307,6 +312,7 @@ check the data we added
     >>> db.close()
     """
 
+
 def test_suite():
     return unittest.TestSuite((
         doctest.DocFileSuite(
@@ -319,4 +325,4 @@ def test_suite():
             setUp=ZODB.tests.util.setUp,
             tearDown=ZODB.tests.util.tearDown,
             checker=checker),
-        ))
+    ))

src/ZODB/MappingStorage.py

@@ -28,9 +28,9 @@ import zope.interface
 
 
 @zope.interface.implementer(
-        ZODB.interfaces.IStorage,
-        ZODB.interfaces.IStorageIteration,
-        )
+    ZODB.interfaces.IStorage,
+    ZODB.interfaces.IStorageIteration,
+)
 class MappingStorage(object):
     """In-memory storage implementation
 
@@ -50,7 +50,8 @@ class MappingStorage(object):
         """
         self.__name__ = name
         self._data = {}                               # {oid->{tid->pickle}}
-        self._transactions = BTrees.OOBTree.OOBTree() # {tid->TransactionRecord}
+        # {tid->TransactionRecord}
+        self._transactions = BTrees.OOBTree.OOBTree()
         self._ltid = ZODB.utils.z64
         self._last_pack = None
         self._lock = ZODB.utils.RLock()
@@ -117,14 +118,14 @@ class MappingStorage(object):
         tids.reverse()
         return [
             dict(
-                time = ZODB.TimeStamp.TimeStamp(tid).timeTime(),
-                tid = tid,
-                serial = tid,
-                user_name = self._transactions[tid].user,
-                description = self._transactions[tid].description,
-                extension = self._transactions[tid].extension,
-                size = len(tid_data[tid])
-                )
+                time=ZODB.TimeStamp.TimeStamp(tid).timeTime(),
+                tid=tid,
+                serial=tid,
+                user_name=self._transactions[tid].user,
+                description=self._transactions[tid].description,
+                extension=self._transactions[tid].extension,
+                size=len(tid_data[tid])
+            )
             for tid in tids]
 
     # ZODB.interfaces.IStorage
@@ -167,8 +168,8 @@ class MappingStorage(object):
         else:
             raise ZODB.POSException.POSKeyError(oid)
 
-
     # ZODB.interfaces.IStorage
+
     @ZODB.utils.locked(opened)
     def loadSerial(self, oid, serial):
         tid_data = self._data.get(oid)
@@ -192,7 +193,7 @@ class MappingStorage(object):
         if not self._data:
             return
 
-        stop = ZODB.TimeStamp.TimeStamp(*time.gmtime(t)[:5]+(t%60,)).raw()
+        stop = ZODB.TimeStamp.TimeStamp(*time.gmtime(t)[:5]+(t % 60,)).raw()
         if self._last_pack is not None and self._last_pack >= stop:
             if self._last_pack == stop:
                 return
@@ -298,7 +299,7 @@ class MappingStorage(object):
 
     # ZODB.interfaces.IStorage
     @ZODB.utils.locked(opened)
-    def tpc_finish(self, transaction, func = lambda tid: None):
+    def tpc_finish(self, transaction, func=lambda tid: None):
         if (transaction is not self._transaction):
             raise ZODB.POSException.StorageTransactionError(
                 "tpc_finish called with wrong transaction")
@@ -332,6 +333,7 @@ class MappingStorage(object):
             raise ZODB.POSException.StorageTransactionError(
                 "tpc_vote called with wrong transaction")
 
+
 class TransactionRecord(object):
 
     status = ' '
@@ -357,11 +359,11 @@ class TransactionRecord(object):
         del self.data[oid]
         return not self.data
 
+
 @zope.interface.implementer(ZODB.interfaces.IStorageRecordInformation)
 class DataRecord(object):
     """Abstract base class for iterator protocol"""
 
-
     version = ''
     data_txn = None
 
@@ -370,5 +372,6 @@ class DataRecord(object):
         self.tid = tid
         self.data = data
 
+
 def DB(*args, **kw):
     return ZODB.DB(MappingStorage(), *args, **kw)

src/ZODB/POSException.py

@@ -18,20 +18,26 @@ $Id$"""
 from ZODB.utils import oid_repr, readable_tid_repr
 
 # BBB: We moved the two transactions to the transaction package
-from transaction.interfaces import TransactionError, TransactionFailedError
+from transaction.interfaces import TransactionError  # noqa: F401 import unused
+from transaction.interfaces import TransactionFailedError  # noqa: F401
 
 import transaction.interfaces
 
+
 def _fmt_undo(oid, reason):
     s = reason and (": %s" % reason) or ""
     return "Undo error %s%s" % (oid_repr(oid), s)
 
+
 def _recon(class_, state):
     err = class_.__new__(class_)
     err.__setstate__(state)
     return err
+
+
 _recon.__no_side_effects__ = True
 
+
 class POSError(Exception):
     """Persistent object system error."""
 
@@ -49,9 +55,10 @@ class POSError(Exception):
         # the args would then get lost, leading to unprintable exceptions
         # and worse. Manually assign to args from the state to be sure
         # this doesn't happen.
-        super(POSError,self).__setstate__(state)
+        super(POSError, self).__setstate__(state)
         self.args = state['args']
 
+
 class POSKeyError(POSError, KeyError):
     """Key not found in database."""
 
@@ -143,6 +150,7 @@ class ConflictError(POSError, transaction.interfaces.TransientError):
     def get_serials(self):
         return self.serials
 
+
 class ReadConflictError(ConflictError):
     """Conflict detected when object was requested to stay unchanged.
 
@@ -156,64 +164,67 @@ class ReadConflictError(ConflictError):
       - object is found to be removed, and
       - there is possibility that database pack was running simultaneously.
     """
+
     def __init__(self, message=None, object=None, serials=None, **kw):
         if message is None:
             message = "database read conflict error"
         ConflictError.__init__(self, message=message, object=object,
                                serials=serials, **kw)
 
+
 class BTreesConflictError(ConflictError):
     """A special subclass for BTrees conflict errors."""
 
-    msgs = [# 0; i2 or i3 bucket split; positions are all -1
-            'Conflicting bucket split',
+    msgs = [
+        # 0; i2 or i3 bucket split; positions are all -1
+        'Conflicting bucket split',
 
-            # 1; keys the same, but i2 and i3 values differ, and both values
-            # differ from i1's value
-            'Conflicting changes',
+        # 1; keys the same, but i2 and i3 values differ, and both values
+        # differ from i1's value
+        'Conflicting changes',
 
-            # 2; i1's value changed in i2, but key+value deleted in i3
-            'Conflicting delete and change',
+        # 2; i1's value changed in i2, but key+value deleted in i3
+        'Conflicting delete and change',
 
-            # 3; i1's value changed in i3, but key+value deleted in i2
-            'Conflicting delete and change',
+        # 3; i1's value changed in i3, but key+value deleted in i2
+        'Conflicting delete and change',
 
-            # 4; i1 and i2 both added the same key, or both deleted the
-            # same key
-            'Conflicting inserts or deletes',
+        # 4; i1 and i2 both added the same key, or both deleted the
+        # same key
+        'Conflicting inserts or deletes',
 
-            # 5;  i2 and i3 both deleted the same key
-            'Conflicting deletes',
+        # 5;  i2 and i3 both deleted the same key
+        'Conflicting deletes',
 
-            # 6; i2 and i3 both added the same key
-            'Conflicting inserts',
+        # 6; i2 and i3 both added the same key
+        'Conflicting inserts',
 
-            # 7; i2 and i3 both deleted the same key, or i2 changed the value
-            # associated with a key and i3 deleted that key
-            'Conflicting deletes, or delete and change',
+        # 7; i2 and i3 both deleted the same key, or i2 changed the value
+        # associated with a key and i3 deleted that key
+        'Conflicting deletes, or delete and change',
 
-            # 8; i2 and i3 both deleted the same key, or i3 changed the value
-            # associated with a key and i2 deleted that key
-            'Conflicting deletes, or delete and change',
+        # 8; i2 and i3 both deleted the same key, or i3 changed the value
+        # associated with a key and i2 deleted that key
+        'Conflicting deletes, or delete and change',
 
-            # 9; i2 and i3 both deleted the same key
-            'Conflicting deletes',
+        # 9; i2 and i3 both deleted the same key
+        'Conflicting deletes',
 
-            # 10; i2 and i3 deleted all the keys, and didn't insert any,
-            # leaving an empty bucket; conflict resolution doesn't have
-            # enough info to unlink an empty bucket from its containing
-            # BTree correctly
-            'Empty bucket from deleting all keys',
+        # 10; i2 and i3 deleted all the keys, and didn't insert any,
+        # leaving an empty bucket; conflict resolution doesn't have
+        # enough info to unlink an empty bucket from its containing
+        # BTree correctly
+        'Empty bucket from deleting all keys',
 
-            # 11; conflicting changes in an internal BTree node
-            'Conflicting changes in an internal BTree node',
+        # 11; conflicting changes in an internal BTree node
+        'Conflicting changes in an internal BTree node',
 
-            # 12; i2 or i3 was empty
-            'Empty bucket in a transaction',
+        # 12; i2 or i3 was empty
+        'Empty bucket in a transaction',
 
-            # 13; delete of first key, which causes change to parent node
-            'Delete of first key',
-            ]
+        # 13; delete of first key, which causes change to parent node
+        'Delete of first key',
+    ]
 
     def __init__(self, p1, p2, p3, reason):
         self.p1 = p1
@@ -226,11 +237,14 @@ class BTreesConflictError(ConflictError):
                                                         self.p2,
                                                         self.p3,
                                                         self.reason)
+
     def __str__(self):
         return "BTrees conflict error at %d/%d/%d: %s" % (
             self.p1, self.p2, self.p3, self.msgs[self.reason])
 
-class DanglingReferenceError(POSError, transaction.interfaces.TransactionError):
+
+class DanglingReferenceError(
+        POSError, transaction.interfaces.TransactionError):
     """An object has a persistent reference to a missing object.
 
     If an object is stored and it has a reference to another object
@@ -258,9 +272,11 @@ class DanglingReferenceError(POSError, transaction.interfaces.TransactionError):
 class VersionError(POSError):
     """An error in handling versions occurred."""
 
+
 class VersionCommitError(VersionError):
     """An invalid combination of versions was used in a version commit."""
 
+
 class VersionLockError(VersionError, transaction.interfaces.TransactionError):
     """Modification to an object modified in an unsaved version.
 
@@ -269,6 +285,7 @@ class VersionLockError(VersionError, transaction.interfaces.TransactionError):
     """
 ############################################################################
 
+
 class UndoError(POSError):
     """An attempt was made to undo a non-undoable transaction."""
 
@@ -279,6 +296,7 @@ class UndoError(POSError):
     def __str__(self):
         return _fmt_undo(self._oid, self._reason)
 
+
 class MultipleUndoErrors(UndoError):
     """Several undo errors occurred during a single transaction."""
 
@@ -290,33 +308,43 @@ class MultipleUndoErrors(UndoError):
     def __str__(self):
         return "\n".join([_fmt_undo(*pair) for pair in self._errs])
 
+
 class StorageError(POSError):
     """Base class for storage based exceptions."""
 
+
 class StorageTransactionError(StorageError):
     """An operation was invoked for an invalid transaction or state."""
 
+
 class StorageSystemError(StorageError):
     """Panic! Internal storage error!"""
 
+
 class MountedStorageError(StorageError):
     """Unable to access mounted storage."""
 
+
 class ReadOnlyError(StorageError):
     """Unable to modify objects in a read-only storage."""
 
+
 class TransactionTooLargeError(StorageTransactionError):
     """The transaction exhausted some finite storage resource."""
 
+
 class ExportError(POSError):
     """An export file doesn't have the right format."""
 
+
 class Unsupported(POSError):
     """A feature was used that is not supported by the storage."""
 
+
 class ReadOnlyHistoryError(POSError):
     """Unable to add or modify objects in an historical connection."""
 
+
 class InvalidObjectReference(POSError):
     """An object contains an invalid reference to another object.
 
@@ -329,6 +357,7 @@ class InvalidObjectReference(POSError):
     TODO:  The exception ought to have a member that is the invalid object.
     """
 
+
 class ConnectionStateError(POSError):
     """A Connection isn't in the required state for an operation.
 

src/ZODB/__init__.py

@@ -12,6 +12,7 @@
 #
 ##############################################################################
 
+from ZODB.DB import DB, connection
 import sys
 
 from persistent import TimeStamp
@@ -24,5 +25,3 @@ sys.modules['ZODB.PersistentMapping'] = sys.modules['persistent.mapping']
 sys.modules['ZODB.PersistentList'] = sys.modules['persistent.list']
 
 del mapping, list, sys
-
-from ZODB.DB import DB, connection

src/ZODB/_compat.py

@@ -11,13 +11,13 @@
 # FOR A PARTICULAR PURPOSE
 #
 ##############################################################################
+from zodbpickle import binary  # noqa: F401 import unused
 import sys
 from six import PY3
 
 IS_JYTHON = sys.platform.startswith('java')
 
 _protocol = 3
-from zodbpickle import binary
 
 if not PY3:
     # Python 2.x
@@ -42,7 +42,8 @@ else:
     # http://bugs.python.org/issue6784
     import zodbpickle.pickle
     HIGHEST_PROTOCOL = 3
-    from _compat_pickle import IMPORT_MAPPING, NAME_MAPPING
+    from _compat_pickle import IMPORT_MAPPING  # noqa: F401 import unused
+    from _compat_pickle import NAME_MAPPING  # noqa: F401 import unused
 
     class Pickler(zodbpickle.pickle.Pickler):
         def __init__(self, f, protocol=None):
@@ -92,6 +93,7 @@ def PersistentPickler(persistent_id, *args, **kwargs):
     p.persistent_id = persistent_id
     return p
 
+
 def PersistentUnpickler(find_global, load_persistent, *args, **kwargs):
     """
     Returns a :class:`Unpickler` that will use the given `find_global` function
@@ -104,7 +106,8 @@ def PersistentUnpickler(find_global, load_persistent, *args, **kwargs):
     if find_global is not None:
         unpickler.find_global = find_global
         try:
-            unpickler.find_class = find_global # PyPy, zodbpickle, the non-c-accelerated version
+            # PyPy, zodbpickle, the non-c-accelerated version
+            unpickler.find_class = find_global
         except AttributeError:
             pass
     if load_persistent is not None:
@@ -118,7 +121,7 @@ try:
     from cStringIO import StringIO as BytesIO
 except ImportError:
     # Python 3.x
-    from io import BytesIO
+    from io import BytesIO  # noqa: F401 import unused
 
 
 try:
@@ -126,14 +129,15 @@ try:
     from base64 import decodebytes, encodebytes
 except ImportError:
     # Python 2.x
-    from base64 import decodestring as decodebytes, encodestring as encodebytes
+    from base64 import decodestring as decodebytes  # noqa: F401 import unused
+    from base64 import encodestring as encodebytes  # noqa: F401 import unused
 
 
 # Python 3.x: ``hasattr()`` swallows only AttributeError.
 def py2_hasattr(obj, name):
     try:
         getattr(obj, name)
-    except:
+    except:  # noqa: E722 do not use bare 'except'
         return False
     return True
 
@@ -151,9 +155,10 @@ else:
 
 try:
     TEXT = unicode
-except NameError: #pragma NO COVER Py3k
+except NameError:  # pragma NO COVER Py3k
     TEXT = str
 
+
 def ascii_bytes(x):
     if isinstance(x, TEXT):
         x = x.encode('ascii')

src/ZODB/blob.py

@@ -35,7 +35,6 @@ from ZODB._compat import BytesIO
 from ZODB._compat import PersistentUnpickler
 from ZODB._compat import decodebytes
 from ZODB._compat import ascii_bytes
-from ZODB._compat import INT_TYPES
 from ZODB._compat import PY3
 
 
@@ -62,20 +61,21 @@ valid_modes = 'r', 'w', 'r+', 'a', 'c'
 # of a weakref when the weakref object dies at the same time
 # as the object it refers to. In other words, this doesn't work:
 #    self._ref = weakref.ref(self, lambda ref: ...)
-# because the function never gets called (https://bitbucket.org/pypy/pypy/issue/2030).
+# because the function never gets called
+# (https://bitbucket.org/pypy/pypy/issue/2030).
 # The Blob class used to use that pattern to clean up uncommitted
 # files; now we use this module-level global (but still keep a
 # reference in the Blob in case we need premature cleanup).
 _blob_close_refs = []
 
+
 @zope.interface.implementer(ZODB.interfaces.IBlob)
 class Blob(persistent.Persistent):
     """A BLOB supports efficient handling of large data within ZODB."""
 
-
     _p_blob_uncommitted = None  # Filename of the uncommitted (dirty) data
-    _p_blob_committed = None    # Filename of the committed data
-    _p_blob_ref = None          # weakreference to self; also in _blob_close_refs
+    _p_blob_committed = None  # Filename of the committed data
+    _p_blob_ref = None  # weakreference to self; also in _blob_close_refs
 
     readers = writers = None
 
@@ -140,11 +140,10 @@ class Blob(persistent.Persistent):
 
         if mode == 'c':
             if (self._p_blob_uncommitted
-                or
-                not self._p_blob_committed
-                or
-                self._p_blob_committed.endswith(SAVEPOINT_SUFFIX)
-                ):
+                    or
+                    not self._p_blob_committed
+                    or
+                    self._p_blob_committed.endswith(SAVEPOINT_SUFFIX)):
                 raise BlobError('Uncommitted changes')
             return self._p_jar._storage.openCommittedBlobFile(
                 self._p_oid, self._p_serial)
@@ -186,7 +185,7 @@ class Blob(persistent.Persistent):
                 if self._p_blob_uncommitted is None:
                     self._create_uncommitted_file()
                 result = BlobFile(self._p_blob_uncommitted, mode, self)
-            else: # 'r+' and 'a'
+            else:  # 'r+' and 'a'
                 if self._p_blob_uncommitted is None:
                     # Create a new working copy
                     self._create_uncommitted_file()
@@ -214,11 +213,10 @@ class Blob(persistent.Persistent):
 
     def committed(self):
         if (self._p_blob_uncommitted
-            or
-            not self._p_blob_committed
-            or
-            self._p_blob_committed.endswith(SAVEPOINT_SUFFIX)
-            ):
+                or
+                not self._p_blob_committed
+                or
+                self._p_blob_committed.endswith(SAVEPOINT_SUFFIX)):
             raise BlobError('Uncommitted changes')
 
         result = self._p_blob_committed
@@ -254,7 +252,7 @@ class Blob(persistent.Persistent):
 
         try:
             rename_or_copy_blob(filename, target, chmod=False)
-        except:
+        except:  # noqa: E722 do not use bare 'except'
             # Recover from the failed consumption: First remove the file, it
             # might exist and mark the pointer to the uncommitted file.
             self._p_blob_uncommitted = None
@@ -317,6 +315,7 @@ class Blob(persistent.Persistent):
         self._p_blob_uncommitted = self._p_blob_ref = None
         return filename
 
+
 class BlobFile(file):
     """A BlobFile that holds a file handle to actual blob data.
 
@@ -348,8 +347,10 @@ class BlobFile(file):
         # prohibit it on all versions.
         raise TypeError("Pickling a BlobFile is not allowed")
 
+
 _pid = str(os.getpid())
 
+
 def log(msg, level=logging.INFO, subsys=_pid, exc_info=False):
     message = "(%s) %s" % (subsys, msg)
     logger.log(level, message, exc_info=exc_info)
@@ -394,8 +395,8 @@ class FilesystemHelper(object):
                 layout = layout_marker.read().strip()
             if layout != self.layout_name:
                 raise ValueError(
-                    "Directory layout `%s` selected for blob directory %s, but "
-                    "marker found for layout `%s`" %
+                    "Directory layout `%s` selected for blob directory %s, but"
+                    " marker found for layout `%s`" %
                     (self.layout_name, self.base_dir, layout))
 
     def isSecure(self, path):
@@ -541,6 +542,7 @@ class NoBlobsFileSystemHelper(object):
 class BlobStorageError(Exception):
     """The blob storage encountered an invalid state."""
 
+
 def auto_layout_select(path):
     # A heuristic to look at a path and determine which directory layout to
     # use.
@@ -593,7 +595,7 @@ class BushyLayout(object):
         directories = [b'0x' + hex_bytes[x:x+2]
                        for x in range(0, 16, 2)]
 
-        if bytes is not str: # py3
+        if bytes is not str:  # py3
             sep_bytes = os.path.sep.encode('ascii')
             path_bytes = sep_bytes.join(directories)
             return path_bytes.decode('ascii')
@@ -618,8 +620,10 @@ class BushyLayout(object):
         filename = "%s%s" % (utils.tid_repr(tid), BLOB_SUFFIX)
         return os.path.join(oid_path, filename)
 
+
 LAYOUTS['bushy'] = BushyLayout()
 
+
 class LawnLayout(BushyLayout):
     """A shallow directory layout for blob directories.
 
@@ -640,8 +644,10 @@ class LawnLayout(BushyLayout):
         except (TypeError, binascii.Error):
             raise ValueError('Not a valid OID path: `%s`' % path)
 
+
 LAYOUTS['lawn'] = LawnLayout()
 
+
 class BlobStorageMixin(object):
     """A mix-in to help storages support blobs."""
 
@@ -738,7 +744,6 @@ class BlobStorage(BlobStorageMixin):
     """A wrapper/proxy storage to support blobs.
     """
 
-
     def __init__(self, base_directory, storage, layout='automatic'):
         assert not ZODB.interfaces.IBlobStorage.providedBy(storage)
         self.__storage = storage
@@ -780,8 +785,8 @@ class BlobStorage(BlobStorageMixin):
 
     def tpc_abort(self, *arg, **kw):
         # We need to override the base storage's abort instead of
-        # providing an _abort method because methods found on the proxied object
-        # aren't rebound to the proxy
+        # providing an _abort method because methods found on the proxied
+        # object aren't rebound to the proxy
         self.__storage.tpc_abort(*arg, **kw)
         self._blob_tpc_abort()
 
@@ -814,7 +819,7 @@ class BlobStorage(BlobStorageMixin):
             if exists:
                 files = os.listdir(oid_path)
                 files.sort()
-                latest = files[-1] # depends on ever-increasing tids
+                latest = files[-1]  # depends on ever-increasing tids
                 files.remove(latest)
                 for f in files:
                     remove_committed(os.path.join(oid_path, f))
@@ -905,7 +910,10 @@ class BlobStorage(BlobStorageMixin):
         res = BlobStorage(base_dir, s)
         return res
 
+
 copied = logging.getLogger('ZODB.blob.copied').debug
+
+
 def rename_or_copy_blob(f1, f2, chmod=True):
     """Try to rename f1 to f2, fallback to copy.
 
@@ -926,6 +934,7 @@ def rename_or_copy_blob(f1, f2, chmod=True):
     if chmod:
         set_not_writable(f2)
 
+
 if sys.platform == 'win32':
     # On Windows, you can't remove read-only files, so make the
     # file writable first.
@@ -952,6 +961,7 @@ def find_global_Blob(module, class_):
     if module == 'ZODB.blob' and class_ == 'Blob':
         return Blob
 
+
 def is_blob_record(record):
     """Check whether a database record is a blob record.
 
@@ -960,7 +970,8 @@ def is_blob_record(record):
 
     """
     if record and (b'ZODB.blob' in record):
-        unpickler = PersistentUnpickler(find_global_Blob, None, BytesIO(record))
+        unpickler = PersistentUnpickler(
+            find_global_Blob, None, BytesIO(record))
 
         try:
             return unpickler.load() is Blob
@@ -971,6 +982,7 @@ def is_blob_record(record):
 
     return False
 
+
 def copyTransactionsFromTo(source, destination):
     for trans in source.iterator():
         destination.tpc_begin(trans, trans.tid, trans.status)
@@ -990,10 +1002,10 @@ def copyTransactionsFromTo(source, destination):
                     with open(name, 'wb') as df:
                         utils.cp(sf, df)
                 destination.restoreBlob(record.oid, record.tid, record.data,
-                                 name, record.data_txn, trans)
+                                        name, record.data_txn, trans)
             else:
                 destination.restore(record.oid, record.tid, record.data,
-                             '', record.data_txn, trans)
+                                    '', record.data_txn, trans)
 
         destination.tpc_vote(trans)
         destination.tpc_finish(trans)
@@ -1001,6 +1013,8 @@ def copyTransactionsFromTo(source, destination):
 
 NO_WRITE = ~ (stat.S_IWUSR | stat.S_IWGRP | stat.S_IWOTH)
 READ_PERMS = stat.S_IRUSR | stat.S_IRGRP | stat.S_IROTH
+
+
 def set_not_writable(path):
     perms = stat.S_IMODE(os.lstat(path).st_mode)
 

src/ZODB/broken.py

@@ -25,6 +25,7 @@ from ZODB._compat import NAME_MAPPING
 
 broken_cache = {}
 
+
 @zope.interface.implementer(ZODB.interfaces.IBroken)
 class Broken(object):
     """Broken object base class
@@ -99,7 +100,6 @@ class Broken(object):
          >>> broken_cache.clear()
        """
 
-
     __Broken_state__ = __Broken_initargs__ = None
 
     __name__ = 'broken object'
@@ -131,6 +131,7 @@ class Broken(object):
     def __setattr__(self, name, value):
         raise BrokenModified("Can't change broken objects")
 
+
 def find_global(modulename, globalname,
                 # These are *not* optimizations. Callers can override these.
                 Broken=Broken, type=type,
@@ -220,6 +221,7 @@ def find_global(modulename, globalname,
     broken_cache[(modulename, globalname)] = class_
     return class_
 
+
 def rebuild(modulename, globalname, *args):
     """Recreate a broken object, possibly recreating the missing class
 
@@ -257,10 +259,12 @@ def rebuild(modulename, globalname, *args):
     class_ = find_global(modulename, globalname)
     return class_.__new__(class_, *args)
 
+
 class BrokenModified(TypeError):
     """Attempt to modify a broken object
     """
 
+
 class PersistentBroken(Broken, persistent.Persistent):
     r"""Persistent broken objects
 
@@ -347,6 +351,7 @@ class PersistentBroken(Broken, persistent.Persistent):
     def __getnewargs__(self):
         return self.__Broken_newargs__
 
+
 def persistentBroken(class_):
     try:
         return class_.__dict__['__Broken_Persistent__']
@@ -356,5 +361,5 @@ def persistentBroken(class_):
                  (PersistentBroken, class_),
                  {'__module__': class_.__module__},
                  )
-            )
+        )
         return class_.__dict__['__Broken_Persistent__']

src/ZODB/config.py

@@ -29,18 +29,21 @@ _db_schema = None
 s_schema_path = os.path.join(ZODB.__path__[0], "storage.xml")
 _s_schema = None
 
+
 def getDbSchema():
     global _db_schema
     if _db_schema is None:
         _db_schema = ZConfig.loadSchema(db_schema_path)
     return _db_schema
 
+
 def getStorageSchema():
     global _s_schema
     if _s_schema is None:
         _s_schema = ZConfig.loadSchema(s_schema_path)
     return _s_schema
 
+
 def databaseFromString(s):
     """Create a database from a database-configuration string.
 
@@ -56,6 +59,7 @@ def databaseFromString(s):
     """
     return databaseFromFile(StringIO(s))
 
+
 def databaseFromFile(f):
     """Create a database from a file object that provides configuration.
 
@@ -64,6 +68,7 @@ def databaseFromFile(f):
     config, handle = ZConfig.loadConfigFile(getDbSchema(), f)
     return databaseFromConfig(config.database)
 
+
 def databaseFromURL(url):
     """Load a database from URL (or file name) that provides configuration.
 
@@ -72,6 +77,7 @@ def databaseFromURL(url):
     config, handler = ZConfig.loadConfig(getDbSchema(), url)
     return databaseFromConfig(config.database)
 
+
 def databaseFromConfig(database_factories):
     databases = {}
     first = None
@@ -82,17 +88,20 @@ def databaseFromConfig(database_factories):
 
     return first
 
+
 def storageFromString(s):
     """Create a storage from a storage-configuration string.
     """
     return storageFromFile(StringIO(s))
 
+
 def storageFromFile(f):
     """Create a storage from a file object providing storage-configuration.
     """
     config, handle = ZConfig.loadConfigFile(getStorageSchema(), f)
     return storageFromConfig(config.storage)
 
+
 def storageFromURL(url):
     """\
     Create a storage from a URL (or file name) providing storage-configuration.
@@ -100,9 +109,11 @@ def storageFromURL(url):
     config, handler = ZConfig.loadConfig(getStorageSchema(), url)
     return storageFromConfig(config.storage)
 
+
 def storageFromConfig(section):
     return section.open()
 
+
 class BaseConfig(object):
     """Object representing a configured storage or database.
 
@@ -124,6 +135,7 @@ class BaseConfig(object):
         """Open and return the storage object."""
         raise NotImplementedError
 
+
 class ZODBDatabase(BaseConfig):
 
     def open(self, databases=None):
@@ -150,21 +162,23 @@ class ZODBDatabase(BaseConfig):
                 cache_size_bytes=section.cache_size_bytes,
                 historical_pool_size=section.historical_pool_size,
                 historical_cache_size=section.historical_cache_size,
-                historical_cache_size_bytes=section.historical_cache_size_bytes,
+                historical_cache_size_bytes=section.historical_cache_size_bytes,  # noqa: E501 line too long
                 historical_timeout=section.historical_timeout,
                 database_name=section.database_name or self.name or '',
                 databases=databases,
                 **options)
-        except:
+        except:  # noqa: E722 do not use bare 'except'
             storage.close()
             raise
 
+
 class MappingStorage(BaseConfig):
 
     def open(self):
         from ZODB.MappingStorage import MappingStorage
         return MappingStorage(self.config.name)
 
+
 class DemoStorage(BaseConfig):
 
     def open(self):
@@ -181,6 +195,7 @@ class DemoStorage(BaseConfig):
         from ZODB.DemoStorage import DemoStorage
         return DemoStorage(self.config.name, base=base, changes=changes)
 
+
 class FileStorage(BaseConfig):
 
     def open(self):
@@ -206,6 +221,7 @@ class FileStorage(BaseConfig):
 
         return FileStorage(config.path, **options)
 
+
 class BlobStorage(BaseConfig):
 
     def open(self):
@@ -225,7 +241,8 @@ class ZEOClient(BaseConfig):
         if self.config.blob_cache_size is not None:
             options['blob_cache_size'] = self.config.blob_cache_size
         if self.config.blob_cache_size_check is not None:
-            options['blob_cache_size_check'] = self.config.blob_cache_size_check
+            options['blob_cache_size_check'] = (
+                self.config.blob_cache_size_check)
         if self.config.client_label is not None:
             options['client_label'] = self.config.client_label
 
@@ -249,6 +266,7 @@ class ZEOClient(BaseConfig):
             realm=self.config.realm,
             **options)
 
+
 class BDBStorage(BaseConfig):
 
     def open(self):
@@ -261,12 +279,14 @@ class BDBStorage(BaseConfig):
             setattr(bconf, name, getattr(self.config, name))
         return storageclass(self.config.envdir, config=bconf)
 
+
 class BDBMinimalStorage(BDBStorage):
 
     def get_storageclass(self):
         import BDBStorage.BDBMinimalStorage
         return BDBStorage.BDBMinimalStorage.BDBMinimalStorage
 
+
 class BDBFullStorage(BDBStorage):
 
     def get_storageclass(self):

src/ZODB/conversionhack.py

@@ -14,21 +14,29 @@
 
 import persistent.mapping
 
+
 class fixer(object):
     def __of__(self, parent):
         def __setstate__(state, self=parent):
-            self._container=state
+            self._container = state
             del self.__setstate__
         return __setstate__
 
-fixer=fixer()
 
-class hack(object): pass
-hack=hack()
+fixer = fixer()
+
+
+class hack(object):
+    pass
+
+
+hack = hack()
+
 
 def __basicnew__():
-    r=persistent.mapping.PersistentMapping()
-    r.__setstate__=fixer
+    r = persistent.mapping.PersistentMapping()
+    r.__setstate__ = fixer
     return r
 
-hack.__basicnew__=__basicnew__
+
+hack.__basicnew__ = __basicnew__

src/ZODB/event.py

@@ -14,5 +14,5 @@
 try:
     from zope.event import notify
 except ImportError:
-    notify = lambda event: None
-
+    def notify(event):
+        return None

src/ZODB/fsIndex.py

@@ -55,17 +55,21 @@ from ZODB._compat import _protocol
 def num2str(n):
     return struct.pack(">Q", n)[2:]
 
+
 def str2num(s):
     return struct.unpack(">Q", b"\000\000" + s)[0]
 
+
 def prefix_plus_one(s):
     num = str2num(s)
     return num2str(num + 1)
 
+
 def prefix_minus_one(s):
     num = str2num(s)
     return num2str(num - 1)
 
+
 def ensure_bytes(s):
     # on Python 3 we might pickle bytes and unpickle unicode strings
     return s.encode('ascii') if not isinstance(s, bytes) else s
@@ -80,11 +84,11 @@ class fsIndex(object):
 
     def __getstate__(self):
         return dict(
-            state_version = 1,
-            _data = [(k, v.toString())
-                     for (k, v) in six.iteritems(self._data)
-                     ]
-            )
+            state_version=1,
+            _data=[(k, v.toString())
+                   for (k, v) in six.iteritems(self._data)
+                   ]
+        )
 
     def __setstate__(self, state):
         version = state.pop('state_version', 0)
@@ -96,13 +100,13 @@ class fsIndex(object):
         self._data = OOBTree([
             (ensure_bytes(k), v)
             for (k, v) in self._data.items()
-            ])
+        ])
 
     def _setstate_1(self, state):
         self._data = OOBTree([
             (ensure_bytes(k), fsBucket().fromString(ensure_bytes(v)))
             for (k, v) in state['_data']
-            ])
+        ])
 
     def __getitem__(self, key):
         assert isinstance(key, bytes)
@@ -246,7 +250,7 @@ class fsIndex(object):
         else:
             try:
                 smallest_suffix = tree.minKey(key[6:])
-            except ValueError: # 'empty tree' (no suffix >= arg)
+            except ValueError:  # 'empty tree' (no suffix >= arg)
                 next_prefix = prefix_plus_one(smallest_prefix)
                 smallest_prefix = self._data.minKey(next_prefix)
                 tree = self._data[smallest_prefix]
@@ -270,7 +274,7 @@ class fsIndex(object):
         else:
             try:
                 biggest_suffix = tree.maxKey(key[6:])
-            except ValueError: # 'empty tree' (no suffix <= arg)
+            except ValueError:  # 'empty tree' (no suffix <= arg)
                 next_prefix = prefix_minus_one(biggest_prefix)
                 biggest_prefix = self._data.maxKey(next_prefix)
                 tree = self._data[biggest_prefix]

src/ZODB/fsrecover.py

@@ -94,12 +94,15 @@ def die(mess='', show_docstring=False):
         print(__doc__ % sys.argv[0], file=sys.stderr)
     sys.exit(1)
 
+
 class ErrorFound(Exception):
     pass
 
+
 def error(mess, *args):
     raise ErrorFound(mess % args)
 
+
 def read_txn_header(f, pos, file_size, outp, ltid):
     # Read the transaction record
     f.seek(pos)
@@ -107,7 +110,7 @@ def read_txn_header(f, pos, file_size, outp, ltid):
     if len(h) < 23:
         raise EOFError
 
-    tid, stl, status, ul, dl, el = unpack(">8s8scHHH",h)
+    tid, stl, status, ul, dl, el = unpack(">8s8scHHH", h)
     status = as_text(status)
     tl = u64(stl)
 
@@ -157,6 +160,7 @@ def read_txn_header(f, pos, file_size, outp, ltid):
 
     return pos, result, tid
 
+
 def truncate(f, pos, file_size, outp):
     """Copy data from pos to end of f to a .trNNN file."""
 
@@ -176,6 +180,7 @@ def truncate(f, pos, file_size, outp):
     f.seek(pos)
     tr.close()
 
+
 def copy(src, dst, n):
     while n:
         buf = src.read(8096)
@@ -186,6 +191,7 @@ def copy(src, dst, n):
         dst.write(buf)
         n -= len(buf)
 
+
 def scan(f, pos):
     """Return a potential transaction location following pos in f.
 
@@ -206,20 +212,21 @@ def scan(f, pos):
 
         s = 0
         while 1:
-            l = data.find(b".", s)
-            if l < 0:
+            l_ = data.find(b".", s)
+            if l_ < 0:
                 pos += len(data)
                 break
             # If we are less than 8 bytes from the end of the
             # string, we need to read more data.
-            s = l + 1
+            s = l_ + 1
             if s > len(data) - 8:
-                pos += l
+                pos += l_
                 break
             tl = u64(data[s:s+8])
             if tl < pos:
                 return pos + s + 8
 
+
 def iprogress(i):
     if i % 2:
         print(".", end=' ')
@@ -227,10 +234,12 @@ def iprogress(i):
         print((i/2) % 10, end=' ')
     sys.stdout.flush()
 
+
 def progress(p):
     for i in range(p):
         iprogress(i)
 
+
 def main():
     try:
         opts, args = getopt.getopt(sys.argv[1:], "fv:pP:")
@@ -256,6 +265,7 @@ def main():
 
     recover(inp, outp, verbose, partial, force, pack)
 
+
 def recover(inp, outp, verbose=0, partial=False, force=False, pack=None):
     print("Recovering", inp, "into", outp)
 
@@ -266,7 +276,7 @@ def recover(inp, outp, verbose=0, partial=False, force=False, pack=None):
     if f.read(4) != ZODB.FileStorage.packed_version:
         die("input is not a file storage")
 
-    f.seek(0,2)
+    f.seek(0, 2)
     file_size = f.tell()
 
     ofs = ZODB.FileStorage.FileStorage(outp, create=1)
@@ -332,11 +342,11 @@ def recover(inp, outp, verbose=0, partial=False, force=False, pack=None):
             for r in txn:
                 if verbose > 1:
                     if r.data is None:
-                        l = "bp"
+                        l_ = "bp"
                     else:
-                        l = len(r.data)
+                        l_ = len(r.data)
 
-                    print("%7d %s %s" % (u64(r.oid), l))
+                    print("%7d %s" % (u64(r.oid), l_))
                 ofs.restore(r.oid, r.tid, r.data, '', r.data_txn,
                             txn)
                 nrec += 1
@@ -370,7 +380,6 @@ def recover(inp, outp, verbose=0, partial=False, force=False, pack=None):
                 prog1 = prog1 + 1
                 iprogress(prog1)
 
-
     bad = file_size - undone - ofs._pos
 
     print("\n%s bytes removed during recovery" % bad)
@@ -385,5 +394,6 @@ def recover(inp, outp, verbose=0, partial=False, force=False, pack=None):
     ofs.close()
     f.close()
 
+
 if __name__ == "__main__":
     main()

src/ZODB/fstools.py

@@ -100,6 +100,7 @@ class TxnHeader(object):
         tlen = u64(self._file.read(8))
         return TxnHeader(self._file, self._pos - (tlen + 8))
 
+
 class DataHeader(object):
     """Object representing a data record header.
 
@@ -111,7 +112,7 @@ class DataHeader(object):
     txn_pos            24-32    position of txn header
     version_len        32-34    length of version (always 0)
     data_len           34-42    length of data
-    
+
     """
 
     def __init__(self, file, pos):
@@ -129,15 +130,16 @@ class DataHeader(object):
         self.prev_rec_pos = u64(prev_rec_pos)
         self.txn_pos = u64(txn_pos)
         self.data_len = u64(data_len)
-        
+
     def next_offset(self):
         """Return offset of next record."""
         off = self._pos + self.data_len
         off += DATA_HDR_LEN
         if self.data_len == 0:
-            off += 8 # backpointer
+            off += 8  # backpointer
         return off
 
+
 def prev_txn(f):
     """Return transaction located before current file position."""
     f.seek(-8, 1)

src/ZODB/interfaces.py

@@ -267,6 +267,7 @@ class IConnection(Interface):
         separate object.
         """
 
+
 class IStorageWrapper(Interface):
     """Storage wrapper interface
 
@@ -296,7 +297,7 @@ class IStorageWrapper(Interface):
 
     This interface may be implemented by storage adapters or other
     intermediaries.  For example, a storage adapter that provides
-    encryption and/or compresssion will apply record transformations
+    encryption and/or compression will apply record transformations
     in it's references method.
     """
 
@@ -343,7 +344,8 @@ class IStorageWrapper(Interface):
         """Return untransformed data
         """
 
-IStorageDB = IStorageWrapper # for backward compatibility
+
+IStorageDB = IStorageWrapper  # for backward compatibility
 
 
 class IDatabase(IStorageDB):
@@ -371,7 +373,6 @@ class IDatabase(IStorageDB):
         this attribute.
         """)
 
-
     def open(transaction_manager=None, serial=''):
         """Return an IConnection object for use by application code.
 
@@ -421,7 +422,6 @@ class IDatabase(IStorageDB):
         also included if they don't conflict with the keys above.
         """
 
-
     def pack(t=None, days=0):
         """Pack the storage, deleting unused object revisions.
 
@@ -433,7 +433,7 @@ class IDatabase(IStorageDB):
         usually an expensive operation.
 
         There are two optional arguments that can be used to set the
-        pack time: t, pack time in seconds since the epcoh, and days,
+        pack time: t, pack time in seconds since the epoch, and days,
         the number of days to subtract from t or from the current
         time if t is not specified.
         """
@@ -539,6 +539,7 @@ class IDatabase(IStorageDB):
         should also close all the Connections.
         """
 
+
 class IStorageTransactionMetaData(Interface):
     """Provide storage transaction meta data.
 
@@ -628,13 +629,13 @@ class IStorage(Interface):
         The format and interpretation of this name is storage
         dependent. It could be a file name, a database name, etc..
 
-        This is used soley for informational purposes.
+        This is used solely for informational purposes.
         """
 
     def getSize():
         """An approximate size of the database, in bytes.
 
-        This is used soley for informational purposes.
+        This is used solely for informational purposes.
         """
 
     def history(oid, size=1):
@@ -660,7 +661,7 @@ class IStorage(Interface):
 
         user_name
             The bytes user identifier, if any (or an empty string) of the
-            user on whos behalf the revision was committed.
+            user on whose behalf the revision was committed.
 
         description
             The bytes transaction description for the transaction that
@@ -704,7 +705,7 @@ class IStorage(Interface):
     def __len__():
         """The approximate number of objects in the storage
 
-        This is used soley for informational purposes.
+        This is used solely for informational purposes.
         """
 
     def loadBefore(oid, tid):
@@ -821,7 +822,7 @@ class IStorage(Interface):
 
         This call is ignored is the storage is not participating in
         two-phase commit or if the given transaction is not the same
-        as the transaction the storage is commiting.
+        as the transaction the storage is committing.
         """
 
     def tpc_begin(transaction):
@@ -837,7 +838,7 @@ class IStorage(Interface):
         current transaction ends (commits or aborts).
         """
 
-    def tpc_finish(transaction, func = lambda tid: None):
+    def tpc_finish(transaction, func=lambda tid: None):
         """Finish the transaction, making any transaction changes permanent.
 
         Changes must be made permanent at this point.
@@ -863,7 +864,7 @@ class IStorage(Interface):
         The argument is the same object passed to tpc_begin.
 
         This call raises a StorageTransactionError if the storage
-        isn't participating in two-phase commit or if it is commiting
+        isn't participating in two-phase commit or if it is committing
         a different transaction.
 
         If a transaction can be committed by a storage, then the
@@ -901,7 +902,7 @@ class IMultiCommitStorage(IStorage):
         the return value is always None.
         """
 
-    def tpc_finish(transaction, func = lambda tid: None):
+    def tpc_finish(transaction, func=lambda tid: None):
         """Finish the transaction, making any transaction changes permanent.
 
         See IStorage.store. For objects implementing this interface,
@@ -954,7 +955,6 @@ class IStorageRestoreable(IStorage):
         #   including the existing FileStorage implementation), that
         #   failed to take into account records after the pack time.
 
-
     def restore(oid, serial, data, version, prev_txn, transaction):
         """Write data already committed in a separate database
 
@@ -996,6 +996,7 @@ class IStorageRecordInformation(Interface):
     data = Attribute("The data record, bytes")
     data_txn = Attribute("The previous transaction id, bytes")
 
+
 class IStorageTransactionInformation(IStorageTransactionMetaData):
     """Provide information about a storage transaction.
 
@@ -1003,7 +1004,7 @@ class IStorageTransactionInformation(IStorageTransactionMetaData):
 
     Note that this may contain a status field used by FileStorage to
     support packing. At some point, this will go away when FileStorage
-    has a better pack algoritm.
+    has a better pack algorithm.
     """
 
     tid = Attribute("Transaction id")
@@ -1034,6 +1035,7 @@ class IStorageIteration(Interface):
 
         """
 
+
 class IStorageUndoable(IStorage):
     """A storage supporting transactional undo.
     """
@@ -1245,6 +1247,7 @@ class IMVCCStorage(IStorage):
         A POSKeyError is raised if there is no record for the object id.
         """
 
+
 class IMVCCPrefetchStorage(IMVCCStorage):
 
     def prefetch(oids):
@@ -1254,6 +1257,7 @@ class IMVCCPrefetchStorage(IMVCCStorage):
         more than once.
         """
 
+
 class IMVCCAfterCompletionStorage(IMVCCStorage):
 
     def afterCompletion():
@@ -1264,6 +1268,7 @@ class IMVCCAfterCompletionStorage(IMVCCStorage):
         See ``transaction.interfaces.ISynchronizer.afterCompletion``.
         """
 
+
 class IStorageCurrentRecordIteration(IStorage):
 
     def record_iternext(next=None):
@@ -1271,6 +1276,7 @@ class IStorageCurrentRecordIteration(IStorage):
 
         Use like this:
 
+            >>> storage = ...
             >>> next = None
             >>> while 1:
             ...     oid, tid, data, next = storage.record_iternext(next)
@@ -1280,24 +1286,26 @@ class IStorageCurrentRecordIteration(IStorage):
 
         """
 
+
 class IExternalGC(IStorage):
 
-   def deleteObject(oid, serial, transaction):
-       """Mark an object as deleted
+    def deleteObject(oid, serial, transaction):
+        """Mark an object as deleted
 
-       This method marks an object as deleted via a new object
-       revision.  Subsequent attempts to load current data for the
-       object will fail with a POSKeyError, but loads for
-       non-current data will suceed if there are previous
-       non-delete records.  The object will be removed from the
-       storage when all not-delete records are removed.
+        This method marks an object as deleted via a new object
+        revision.  Subsequent attempts to load current data for the
+        object will fail with a POSKeyError, but loads for
+        non-current data will succeed if there are previous
+        non-delete records.  The object will be removed from the
+        storage when all not-delete records are removed.
 
-       The serial argument must match the most recently committed
-       serial for the object. This is a seat belt.
+        The serial argument must match the most recently committed
+        serial for the object. This is a seat belt.
+
+        This method can only be called in the first phase of 2-phase
+        commit.
+        """
 
-       This method can only be called in the first phase of 2-phase
-       commit.
-       """
 
 class ReadVerifyingStorage(IStorage):
 
@@ -1315,6 +1323,7 @@ class ReadVerifyingStorage(IStorage):
         through the end of the transaction.
         """
 
+
 class IBlob(Interface):
     """A BLOB supports efficient handling of large data within ZODB."""
 
@@ -1325,7 +1334,7 @@ class IBlob(Interface):
 
         mode: Mode to open the file with. Possible values: r,w,r+,a,c
 
-        The mode 'c' is similar to 'r', except that an orinary file
+        The mode 'c' is similar to 'r', except that an ordinary file
         object is returned and may be used in a separate transaction
         and after the blob's database connection has been closed.
 
@@ -1335,8 +1344,8 @@ class IBlob(Interface):
         """Return a file name for committed data.
 
         The returned file name may be opened for reading or handed to
-        other processes for reading.  The file name isn't guarenteed
-        to be valid indefinately.  The file may be removed in the
+        other processes for reading.  The file name isn't guaranteed
+        to be valid indefinitely.  The file may be removed in the
         future as a result of garbage collection depending on system
         configuration.
 
@@ -1412,6 +1421,7 @@ class IBlobStorage(Interface):
         If Blobs use this, then commits can be performed with a simple rename.
         """
 
+
 class IBlobStorageRestoreable(IBlobStorage, IStorageRestoreable):
 
     def restoreBlob(oid, serial, data, blobfilename, prev_txn, transaction):
@@ -1446,6 +1456,7 @@ class IBroken(Interface):
     __Broken_initargs__ = Attribute("Arguments passed to __init__.")
     __Broken_state__ = Attribute("Value passed to __setstate__.")
 
+
 class BlobError(Exception):
     pass
 

src/ZODB/mvccadapter.py

@@ -12,6 +12,7 @@ import zope.interface
 from . import interfaces, serialize, POSException
 from .utils import p64, u64, Lock, oid_repr, tid_repr
 
+
 class Base(object):
 
     _copy_methods = (
@@ -19,7 +20,7 @@ class Base(object):
         'loadBlob', 'openCommittedBlobFile',
         'isReadOnly', 'supportsUndo', 'undoLog', 'undoInfo',
         'temporaryDirectory',
-        )
+    )
 
     def __init__(self, storage):
         self._storage = storage
@@ -37,6 +38,7 @@ class Base(object):
     def __len__(self):
         return len(self._storage)
 
+
 class MVCCAdapter(Base):
 
     def __init__(self, storage):
@@ -63,6 +65,7 @@ class MVCCAdapter(Base):
             self._instances.remove(instance)
 
     closed = False
+
     def close(self):
         if not self.closed:
             self.closed = True
@@ -92,14 +95,15 @@ class MVCCAdapter(Base):
     def pack(self, pack_time, referencesf):
         return self._storage.pack(pack_time, referencesf)
 
+
 class MVCCAdapterInstance(Base):
 
     _copy_methods = Base._copy_methods + (
         'loadSerial', 'new_oid', 'tpc_vote',
         'checkCurrentSerialInTransaction', 'tpc_abort',
-        )
+    )
 
-    _start = None # Transaction start time
+    _start = None  # Transaction start time
     _ltid = b''   # Last storage transaction id
 
     def __init__(self, base):
@@ -107,7 +111,7 @@ class MVCCAdapterInstance(Base):
         Base.__init__(self, base._storage)
         self._lock = Lock()
         self._invalidations = set()
-        self._sync = getattr(self._storage, 'sync', lambda : None)
+        self._sync = getattr(self._storage, 'sync', lambda: None)
 
     def release(self):
         self._base._release(self)
@@ -175,8 +179,8 @@ class MVCCAdapterInstance(Base):
             # into account, and raise ReadConflictError only in the presence of
             # database being simultaneously updated from back of its log.
             raise POSException.ReadConflictError(
-                    "load %s @%s: object deleted, likely by simultaneous pack" %
-                    (oid_repr(oid), tid_repr(p64(u64(self._start) - 1))))
+                "load %s @%s: object deleted, likely by simultaneous pack" %
+                (oid_repr(oid), tid_repr(p64(u64(self._start) - 1))))
 
         return r[:2]
 
@@ -189,8 +193,8 @@ class MVCCAdapterInstance(Base):
             else:
                 raise
 
-    _modified = None # Used to keep track of oids modified within a
-                     # transaction, so we can invalidate them later.
+    _modified = None  # Used to keep track of oids modified within a
+    # transaction, so we can invalidate them later.
 
     def tpc_begin(self, transaction):
         self._storage.tpc_begin(transaction)
@@ -205,7 +209,7 @@ class MVCCAdapterInstance(Base):
             oid, serial, data, blobfilename, '', transaction)
         self._modified.add(oid)
 
-    def tpc_finish(self, transaction, func = lambda tid: None):
+    def tpc_finish(self, transaction, func=lambda tid: None):
         modified = self._modified
         self._modified = None
 
@@ -216,9 +220,11 @@ class MVCCAdapterInstance(Base):
 
         return self._storage.tpc_finish(transaction, invalidate_finish)
 
+
 def read_only_writer(self, *a, **kw):
     raise POSException.ReadOnlyError
 
+
 class HistoricalStorageAdapter(Base):
     """Adapt a storage to a historical storage
     """
@@ -226,7 +232,7 @@ class HistoricalStorageAdapter(Base):
     _copy_methods = Base._copy_methods + (
         'loadSerial', 'tpc_begin', 'tpc_finish', 'tpc_abort', 'tpc_vote',
         'checkCurrentSerialInTransaction',
-        )
+    )
 
     def __init__(self, storage, before=None):
         Base.__init__(self, storage)
@@ -267,7 +273,7 @@ class UndoAdapterInstance(Base):
 
     _copy_methods = Base._copy_methods + (
         'tpc_abort',
-        )
+    )
 
     def __init__(self, base):
         self._base = base
@@ -293,7 +299,7 @@ class UndoAdapterInstance(Base):
         if result:
             self._undone.update(result)
 
-    def tpc_finish(self, transaction, func = lambda tid: None):
+    def tpc_finish(self, transaction, func=lambda tid: None):
 
         def invalidate_finish(tid):
             self._base._invalidate_finish(tid, self._undone, None)

src/ZODB/persistentclass.py

@@ -63,6 +63,7 @@ class _p_DataDescr(object):
     def __delete__(self, inst):
         raise AttributeError(self.__name__)
 
+
 class _p_oid_or_jar_Descr(_p_DataDescr):
     # Special descr for _p_oid and _p_jar that loads
     # state when set if both are set and _p_changed is None
@@ -78,11 +79,11 @@ class _p_oid_or_jar_Descr(_p_DataDescr):
 
         jar = get('_p_jar')
         if (jar is not None
-            and get('_p_oid') is not None
-            and get('_p_changed') is None
-            ):
+                and get('_p_oid') is not None
+                and get('_p_changed') is None):
             jar.setstate(inst)
 
+
 class _p_ChangedDescr(object):
     # descriptor to handle special weird semantics of _p_changed
 
@@ -99,6 +100,7 @@ class _p_ChangedDescr(object):
     def __delete__(self, inst):
         inst._p_invalidate()
 
+
 class _p_MethodDescr(object):
     """Provide unassignable class attributes
     """
@@ -120,6 +122,7 @@ class _p_MethodDescr(object):
 
 special_class_descrs = '__dict__', '__weakref__'
 
+
 class PersistentMetaClass(type):
 
     _p_jar = _p_oid_or_jar_Descr('_p_jar')
@@ -148,8 +151,8 @@ class PersistentMetaClass(type):
             and
             (get('_p_oid') is not None)
             and
-            (get('_p_changed') == False)
-            ):
+            (get('_p_changed') is False)
+        ):
 
             self._p_changed = True
             data_manager.register(self)
@@ -177,7 +180,6 @@ class PersistentMetaClass(type):
 
     _p_invalidate = _p_MethodDescr(_p_invalidate)
 
-
     def __getstate__(self):
         return (self.__bases__,
                 dict([(k, v) for (k, v) in self.__dict__.items()
@@ -185,7 +187,7 @@ class PersistentMetaClass(type):
                               or k.startswith('_v_')
                               or k in special_class_descrs
                               )
-                     ]),
+                      ]),
                 )
 
     __getstate__ = _p_MethodDescr(__getstate__)

src/ZODB/scripts/analyze.py

@@ -9,7 +9,6 @@ from ZODB.FileStorage import FileStorage
 from ZODB._compat import PersistentUnpickler, BytesIO
 
 
-
 class FakeError(Exception):
     def __init__(self, module, name):
         Exception.__init__(self)
@@ -41,20 +40,22 @@ class Report(object):
         self.FOIDS = 0
         self.FBYTES = 0
 
+
 def shorten(s, n):
-    l = len(s)
-    if l <= n:
+    length = len(s)
+    if length <= n:
         return s
-    while len(s) + 3 > n: # account for ...
+    while len(s) + 3 > n:  # account for ...
         i = s.find(".")
         if i == -1:
             # In the worst case, just return the rightmost n bytes
             return s[-n:]
         else:
             s = s[i + 1:]
-            l = len(s)
+            length = len(s)
     return "..." + s
 
+
 def report(rep):
     print("Processed %d records in %d transactions" % (rep.OIDS, rep.TIDS))
     print("Average record size is %7.2f bytes" % (rep.DBYTES * 1.0 / rep.OIDS))
@@ -63,8 +64,8 @@ def report(rep):
 
     print("Types used:")
     fmt = "%-46s %7s %9s %6s %7s"
-    fmtp = "%-46s %7d %9d %5.1f%% %7.2f" # per-class format
-    fmts = "%46s %7d %8dk %5.1f%% %7.2f" # summary format
+    fmtp = "%-46s %7d %9d %5.1f%% %7.2f"  # per-class format
+    fmts = "%46s %7d %8dk %5.1f%% %7.2f"  # summary format
     print(fmt % ("Class Name", "Count", "TBytes", "Pct", "AvgSize"))
     print(fmt % ('-'*46, '-'*7, '-'*9, '-'*5, '-'*7))
     typemap = sorted(rep.TYPEMAP)
@@ -76,8 +77,9 @@ def report(rep):
                       pct, rep.TYPESIZE[t] * 1.0 / rep.TYPEMAP[t]))
 
     print(fmt % ('='*46, '='*7, '='*9, '='*5, '='*7))
-    print("%46s %7d %9s %6s %6.2fk" % ('Total Transactions', rep.TIDS, ' ',
-        ' ', rep.DBYTES * 1.0 / rep.TIDS / 1024.0))
+    print("%46s %7d %9s %6s %6.2fk" % (
+        'Total Transactions', rep.TIDS, ' ', ' ',
+        rep.DBYTES * 1.0 / rep.TIDS / 1024.0))
     print(fmts % ('Total Records', rep.OIDS, rep.DBYTES / 1024.0, cumpct,
                   rep.DBYTES * 1.0 / rep.OIDS))
 
@@ -89,6 +91,7 @@ def report(rep):
                       rep.FBYTES * 100.0 / rep.DBYTES,
                       rep.FBYTES * 1.0 / rep.FOIDS))
 
+
 def analyze(path):
     fs = FileStorage(path, read_only=1)
     fsi = fs.iterator()
@@ -97,11 +100,13 @@ def analyze(path):
         analyze_trans(report, txn)
     return report
 
+
 def analyze_trans(report, txn):
     report.TIDS += 1
     for rec in txn:
         analyze_rec(report, rec)
 
+
 def get_type(record):
     try:
         unpickled = FakeUnpickler(BytesIO(record.data)).load()
@@ -114,6 +119,7 @@ def get_type(record):
     else:
         return str(classinfo)
 
+
 def analyze_rec(report, record):
     oid = record.oid
     report.OIDS += 1
@@ -121,7 +127,7 @@ def analyze_rec(report, record):
         # No pickle -- aborted version or undo of object creation.
         return
     try:
-        size = len(record.data) # Ignores various overhead
+        size = len(record.data)  # Ignores various overhead
         report.DBYTES += size
         if oid not in report.OIDMAP:
             type = get_type(record)
@@ -142,6 +148,7 @@ def analyze_rec(report, record):
     except Exception as err:
         print(err)
 
+
 if __name__ == "__main__":
     path = sys.argv[1]
     report(analyze(path))

src/ZODB/scripts/checkbtrees.py

@@ -19,18 +19,21 @@ oids_seen = {}
 
 # Append (obj, path) to L if and only if obj is a persistent object
 # and we haven't seen it before.
+
+
 def add_if_new_persistent(L, obj, path):
     global oids_seen
 
-    getattr(obj, '_', None) # unghostify
+    getattr(obj, '_', None)  # unghostify
     if hasattr(obj, '_p_oid'):
         oid = obj._p_oid
         if oid not in oids_seen:
             L.append((obj, path))
             oids_seen[oid] = 1
 
+
 def get_subobjects(obj):
-    getattr(obj, '_', None) # unghostify
+    getattr(obj, '_', None)  # unghostify
     sub = []
     try:
         attrs = obj.__dict__.items()
@@ -55,22 +58,23 @@ def get_subobjects(obj):
     while 1:
         try:
             elt = obj[i]
-        except:
+        except:  # noqa: E722 do not use bare 'except'
             break
         sub.append(("[%d]" % i, elt))
         i += 1
 
     return sub
 
+
 def main(fname=None):
     if fname is None:
         import sys
         try:
             fname, = sys.argv[1:]
-        except:
+        except:  # noqa: E722 do not use bare 'except'
             print(__doc__)
             sys.exit(2)
-        
+
     fs = FileStorage(fname, read_only=1)
     cn = ZODB.DB(fs).open()
     rt = cn.root()
@@ -116,5 +120,6 @@ def main(fname=None):
 
     print("total", len(fs._index), "found", found)
 
+
 if __name__ == "__main__":
     main()

src/ZODB/scripts/fsoids.py

@@ -43,9 +43,11 @@ import sys
 
 from ZODB.FileStorage.fsoids import Tracer
 
+
 def usage():
     print(__doc__)
 
+
 def main():
     import getopt
 
@@ -64,7 +66,7 @@ def main():
 
     c = Tracer(args[0])
     for oid in args[1:]:
-        as_int = int(oid, 0) # 0 == auto-detect base
+        as_int = int(oid, 0)  # 0 == auto-detect base
         c.register_oids(as_int)
     if path is not None:
         for line in open(path):
@@ -75,5 +77,6 @@ def main():
     c.run()
     c.report()
 
+
 if __name__ == "__main__":
     main()

src/ZODB/scripts/fsrefs.py

@@ -74,6 +74,8 @@ from BTrees.QQBTree import QQBTree
 # There's a problem with oid.  'data' is its pickle, and 'serial' its
 # serial number.  'missing' is a list of (oid, class, reason) triples,
 # explaining what the problem(s) is(are).
+
+
 def report(oid, data, serial, missing):
     from_mod, from_class = get_pickle_metadata(data)
     if len(missing) > 1:
@@ -92,6 +94,7 @@ def report(oid, data, serial, missing):
         print("\toid %s %s: %r" % (oid_repr(oid), reason, description))
     print()
 
+
 def main(path=None):
     verbose = 0
     if path is None:
@@ -105,7 +108,6 @@ def main(path=None):
 
         path, = args
 
-
     fs = FileStorage(path, read_only=1)
 
     # Set of oids in the index that failed to load due to POSKeyError.
@@ -122,7 +124,7 @@ def main(path=None):
     # build {pos -> oid} index that is reverse to {oid -> pos} fs._index
     # we'll need this to iterate objects in order of ascending file position to
     # optimize disk IO.
-    pos2oid = QQBTree() # pos -> u64(oid)
+    pos2oid = QQBTree()  # pos -> u64(oid)
     for oid, pos in fs._index.iteritems():
         pos2oid[pos] = u64(oid)
 
@@ -137,14 +139,14 @@ def main(path=None):
             raise
         except POSKeyError:
             undone[oid] = 1
-        except:
+        except:  # noqa: E722 do not use bare 'except'
             if verbose:
                 traceback.print_exc()
             noload[oid] = 1
 
     # pass 2: go through all objects again and verify that their references do
-    # not point to problematic object set. Iterate objects in order of ascending
-    # file position to optimize disk IO.
+    # not point to problematic object set. Iterate objects in order of
+    # ascending file position to optimize disk IO.
     inactive = noload.copy()
     inactive.update(undone)
     for oid64 in pos2oid.itervalues():
@@ -153,7 +155,7 @@ def main(path=None):
             continue
         data, serial = load_current(fs, oid)
         refs = get_refs(data)
-        missing = [] # contains 3-tuples of oid, klass-metadata, reason
+        missing = []  # contains 3-tuples of oid, klass-metadata, reason
         for ref, klass in refs:
             if klass is None:
                 klass = '<unknown>'
@@ -166,5 +168,6 @@ def main(path=None):
         if missing:
             report(oid, data, serial, missing)
 
+
 if __name__ == "__main__":
     main()

src/ZODB/scripts/fsstats.py

@@ -9,6 +9,7 @@ from six.moves import filter
 rx_txn = re.compile(r"tid=([0-9a-f]+).*size=(\d+)")
 rx_data = re.compile(r"oid=([0-9a-f]+) size=(\d+) class=(\S+)")
 
+
 def sort_byhsize(seq, reverse=False):
     L = [(v.size(), k, v) for k, v in seq]
     L.sort()
@@ -16,6 +17,7 @@ def sort_byhsize(seq, reverse=False):
         L.reverse()
     return [(k, v) for n, k, v in L]
 
+
 class Histogram(dict):
 
     def add(self, size):
@@ -93,6 +95,7 @@ class Histogram(dict):
                 i * binsize, n, p, pc, "*" * (n // dot)))
         print()
 
+
 def class_detail(class_size):
     # summary of classes
     fmt = "%5s %6s %6s %6s   %-50.50s"
@@ -110,6 +113,7 @@ def class_detail(class_size):
             continue
         h.report("Object size for %s" % klass, usebins=True)
 
+
 def revision_detail(lifetimes, classes):
     # Report per-class details for any object modified more than once
     for name, oids in six.iteritems(classes):
@@ -124,17 +128,18 @@ def revision_detail(lifetimes, classes):
         if keep:
             h.report("Number of revisions for %s" % name, binsize=10)
 
+
 def main(path=None):
     if path is None:
         path = sys.argv[1]
-    txn_objects = Histogram() # histogram of txn size in objects
-    txn_bytes = Histogram() # histogram of txn size in bytes
-    obj_size = Histogram() # histogram of object size
-    n_updates = Histogram() # oid -> num updates
-    n_classes = Histogram() # class -> num objects
-    lifetimes = {} # oid -> list of tids
-    class_size = {} # class -> histogram of object size
-    classes = {} # class -> list of oids
+    txn_objects = Histogram()  # histogram of txn size in objects
+    txn_bytes = Histogram()  # histogram of txn size in bytes
+    obj_size = Histogram()  # histogram of object size
+    n_updates = Histogram()  # oid -> num updates
+    n_classes = Histogram()  # class -> num objects
+    lifetimes = {}  # oid -> list of tids
+    class_size = {}  # class -> histogram of object size
+    classes = {}  # class -> list of oids
 
     MAX = 0
     objects = 0
@@ -203,5 +208,6 @@ def main(path=None):
 
     class_detail(class_size)
 
+
 if __name__ == "__main__":
     main()

src/ZODB/scripts/fstail.py

@@ -25,6 +25,7 @@ try:
 except ImportError:
     from sha import sha as sha1
 
+
 def main(path, ntxn):
     with open(path, "rb") as f:
         f.seek(0, 2)
@@ -32,7 +33,6 @@ def main(path, ntxn):
         i = ntxn
         while th and i > 0:
             hash = sha1(th.get_raw_data()).digest()
-            l = len(str(th.get_timestamp())) + 1
             th.read_meta()
             print("%s: hash=%s" % (th.get_timestamp(),
                                    binascii.hexlify(hash).decode()))
@@ -42,6 +42,7 @@ def main(path, ntxn):
             th = th.prev_txn()
             i -= 1
 
+
 def Main():
     ntxn = 10
     opts, args = getopt.getopt(sys.argv[1:], "n:")
@@ -51,5 +52,6 @@ def Main():
             ntxn = int(v)
     main(path, ntxn)
 
+
 if __name__ == "__main__":
     Main()

src/ZODB/scripts/fstest.py

@@ -41,13 +41,16 @@ import struct
 import sys
 from ZODB._compat import FILESTORAGE_MAGIC
 
+
 class FormatError(ValueError):
     """There is a problem with the format of the FileStorage."""
 
+
 class Status(object):
     checkpoint = b'c'
     undone = b'u'
 
+
 packed_version = FILESTORAGE_MAGIC
 
 TREC_HDR_LEN = 23
@@ -55,6 +58,7 @@ DREC_HDR_LEN = 42
 
 VERBOSE = 0
 
+
 def hexify(s):
     r"""Format an 8-bit string as hex
 
@@ -64,17 +68,20 @@ def hexify(s):
     """
     return '0x' + binascii.hexlify(s).decode()
 
+
 def chatter(msg, level=1):
     if VERBOSE >= level:
         sys.stdout.write(msg)
 
+
 def U64(v):
     """Unpack an 8-byte string as a 64-bit long"""
-    h, l = struct.unpack(">II", v)
+    h, l_ = struct.unpack(">II", v)
     if h:
-        return (h << 32) + l
+        return (h << 32) + l_
     else:
-        return l
+        return l_
+
 
 def check(path):
     with open(path, 'rb') as file:
@@ -87,7 +94,7 @@ def check(path):
             raise FormatError("invalid file header")
 
         pos = 4
-        tid = b'\000' * 8 # lowest possible tid to start
+        tid = b'\000' * 8  # lowest possible tid to start
         i = 0
         while pos:
             _pos = pos
@@ -106,7 +113,7 @@ def check_trec(path, file, pos, ltid, file_size):
     used for generating error messages.
     """
 
-    h = file.read(TREC_HDR_LEN) #XXX must be bytes under Py3k
+    h = file.read(TREC_HDR_LEN)  # XXX must be bytes under Py3k
     if not h:
         return None, None
     if len(h) != TREC_HDR_LEN:
@@ -120,7 +127,7 @@ def check_trec(path, file, pos, ltid, file_size):
                           (path, pos, hexify(tid), hexify(ltid)))
     ltid = tid
 
-    tl = U64(stl) # transaction record length - 8
+    tl = U64(stl)  # transaction record length - 8
     if pos + tl + 8 > file_size:
         raise FormatError("%s truncated possibly because of"
                           " damaged records at %s" % (path, pos))
@@ -140,7 +147,7 @@ def check_trec(path, file, pos, ltid, file_size):
 
     if status != Status.undone:
         pos = tpos + tmeta_len
-        file.read(ul + dl + el) # skip transaction metadata
+        file.read(ul + dl + el)  # skip transaction metadata
 
         i = 0
         while pos < tend:
@@ -162,6 +169,7 @@ def check_trec(path, file, pos, ltid, file_size):
     pos = tend + 8
     return pos, tid
 
+
 def check_drec(path, file, pos, tpos, tid):
     """Check a data record for the current transaction record"""
 
@@ -170,7 +178,7 @@ def check_drec(path, file, pos, tpos, tid):
         raise FormatError("%s truncated at %s" % (path, pos))
     oid, serial, _prev, _tloc, vlen, _plen = (
         struct.unpack(">8s8s8s8sH8s", h))
-    prev = U64(_prev)
+    U64(_prev)
     tloc = U64(_tloc)
     plen = U64(_plen)
     dlen = DREC_HDR_LEN + (plen or 8)
@@ -178,8 +186,8 @@ def check_drec(path, file, pos, tpos, tid):
     if vlen:
         dlen = dlen + 16 + vlen
         file.seek(8, 1)
-        pv = U64(file.read(8))
-        file.seek(vlen, 1) # skip the version data
+        U64(file.read(8))
+        file.seek(vlen, 1)  # skip the version data
 
     if tloc != tpos:
         raise FormatError("%s data record exceeds transaction record "
@@ -195,9 +203,11 @@ def check_drec(path, file, pos, tpos, tid):
 
     return pos, oid
 
+
 def usage():
     sys.exit(__doc__)
 
+
 def main(args=None):
     if args is None:
         args = sys.argv[1:]
@@ -221,5 +231,6 @@ def main(args=None):
 
     chatter("no errors detected")
 
+
 if __name__ == "__main__":
     main()

src/ZODB/scripts/manual_tests/testfstest.py

@@ -6,12 +6,12 @@ Note:  To run this test script fstest.py must be on your PYTHONPATH.
 from cStringIO import StringIO
 import re
 import struct
-import unittest
 import ZODB.tests.util
 
 import fstest
 from fstest import FormatError, U64
 
+
 class TestCorruptedFS(ZODB.tests.util.TestCase):
 
     f = open('test-checker.fs', 'rb')
@@ -117,7 +117,7 @@ class TestCorruptedFS(ZODB.tests.util.TestCase):
         self._file.write(data)
         buf = self._datafs.read(tl - 8)
         self._file.write(buf[0])
-        assert tl <= 1<<16, "can't use this transaction for this test"
+        assert tl <= 1 << 16, "can't use this transaction for this test"
         self._file.write("\777\777")
         self._file.write(buf[3:])
         self.detectsError("invalid transaction header")
@@ -172,6 +172,3 @@ class TestCorruptedFS(ZODB.tests.util.TestCase):
         self._file.write("\000" * 4 + "\077" + "\000" * 3)
         self._file.write(data[32:])
         self.detectsError("record exceeds transaction")
-
-if __name__ == "__main__":
-    unittest.main()

src/ZODB/scripts/migrate.py

@@ -82,7 +82,7 @@ import profile
 
 from persistent.timestamp import TimeStamp
 from ZODB import utils
-from ZODB import StorageTypes # XXX: This import does not exist
+from ZODB import StorageTypes  # XXX: This import does not exist
 
 
 PROGRAM = sys.argv[0]
@@ -130,7 +130,7 @@ def main():
         elif opt in ('-v', '--verbose'):
             options.verbose += 1
         elif opt in ('-T', '--storage_types'):
-            print_types()
+            print('Unknown option.')
             sys.exit(0)
         elif opt in ('-S', '--stype'):
             options.stype = arg
@@ -247,16 +247,16 @@ def doit(srcdb, dstdb, options):
             t = TimeStamp(tid)
             if t <= ts:
                 if ok:
-                    print((
-                        'Time stamps are out of order %s, %s' % (ts, t)), file=sys.stderr)
+                    print('Time stamps are out of order %s, %s' % (ts, t),
+                          file=sys.stderr)
                     ok = False
                     ts = t.laterThan(ts)
                     tid = ts.raw()
                 else:
                     ts = t
                     if not ok:
-                        print((
-                            'Time stamps are back in order %s' % t), file=sys.stderr)
+                        print('Time stamps are back in order %s' % t,
+                              file=sys.stderr)
                         ok = True
         if verbose > 1:
             print(ts)
@@ -310,7 +310,7 @@ def doit(srcdb, dstdb, options):
             tidstr = utils.U64(tid)
             format = "%4d. %20s %6d %8d %6.4f %6.4f %6.4f %6.4f %6.4f"
         print(format % (skipper, tidstr, objects, size,
-                                  t4-t0, t1-t0, t2-t1, t3-t2, t4-t3), file=outfp)
+                        t4-t0, t1-t0, t2-t1, t3-t2, t4-t3), file=outfp)
         total_pickle_size += size
         total_object_count += objects
 

src/ZODB/scripts/migrateblobs.py

@@ -23,17 +23,17 @@ from ZODB.blob import FilesystemHelper
 from ZODB.utils import oid_repr
 
 
-def link_or_copy(f1, f2):
-    try:
-        os.link(f1, f2)
-    except OSError:
-        shutil.copy(f1, f2)
-
 # Check if we actually have link
 try:
     os.link
 except AttributeError:
     link_or_copy = shutil.copy
+else:
+    def link_or_copy(f1, f2):
+        try:
+            os.link(f1, f2)
+        except OSError:
+            shutil.copy(f1, f2)
 
 
 def migrate(source, dest, layout):

src/ZODB/scripts/netspace.py

@@ -13,6 +13,7 @@ from ZODB.utils import U64, get_pickle_metadata, load_current
 from ZODB.serialize import referencesf
 from six.moves import filter
 
+
 def find_paths(root, maxdist):
     """Find Python attribute traversal paths for objects to maxdist distance.
 
@@ -37,7 +38,7 @@ def find_paths(root, maxdist):
         if oid is not None:
             paths[oid] = path
         if dist < maxdist:
-            getattr(obj, 'foo', None) # unghostify
+            getattr(obj, 'foo', None)  # unghostify
             try:
                 items = obj.__dict__.items()
             except AttributeError:
@@ -48,6 +49,7 @@ def find_paths(root, maxdist):
 
     return paths
 
+
 def main(path):
     fs = FileStorage(path, read_only=1)
     if PACK:
@@ -60,6 +62,7 @@ def main(path):
     def total_size(oid):
         cache = {}
         cache_size = 1000
+
         def _total_size(oid, seen):
             v = cache.get(oid)
             if v is not None:
@@ -91,10 +94,11 @@ def main(path):
     for oid in keys:
         data, serialno = load_current(fs, oid)
         mod, klass = get_pickle_metadata(data)
-        refs = referencesf(data)
+        referencesf(data)
         path = paths.get(oid, '-')
         print(fmt % (U64(oid), len(data), total_size(oid), path, mod, klass))
 
+
 def Main():
     import sys
     import getopt
@@ -122,5 +126,6 @@ def Main():
             VERBOSE += 1
     main(path)
 
+
 if __name__ == "__main__":
     Main()

src/ZODB/scripts/referrers.py

@@ -18,6 +18,7 @@ $Id$
 
 from ZODB.serialize import referencesf
 
+
 def referrers(storage):
     result = {}
     for transaction in storage.iterator():

src/ZODB/scripts/repozo.py

@@ -85,6 +85,7 @@ Options for -V/--verify:
         Verify file sizes only (skip md5 checksums).
 """
 from __future__ import print_function
+import re
 import os
 import shutil
 import sys
@@ -176,7 +177,7 @@ def parseargs(argv):
                                     'date=',
                                     'output=',
                                     'with-verification',
-                                   ])
+                                    ])
     except getopt.error as msg:
         usage(1, msg)
 
@@ -299,6 +300,8 @@ def fsync(afile):
 # Return the total number of bytes read == the total number of bytes
 # passed in all to func().  Leaves the file position just after the
 # last byte read.
+
+
 def dofile(func, fp, n=None):
     bytesread = 0
     while n is None or n > 0:
@@ -320,6 +323,7 @@ def dofile(func, fp, n=None):
 def checksum(fp, n):
     # Checksum the first n bytes of the specified file
     sum = md5()
+
     def func(data):
         sum.update(data)
     dofile(func, fp, n)
@@ -336,6 +340,7 @@ def file_size(fp):
 def checksum_and_size(fp):
     # Checksum and return it with the size of the file
     sum = md5()
+
     def func(data):
         sum.update(data)
     size = dofile(func, fp, None)
@@ -374,6 +379,7 @@ def concat(files, ofp=None):
     # given.  Return the number of bytes written and the md5 checksum of the
     # bytes.
     sum = md5()
+
     def func(data):
         sum.update(data)
         if ofp:
@@ -393,6 +399,7 @@ def concat(files, ofp=None):
 def gen_filedate(options):
     return getattr(options, 'test_now', time.gmtime()[:6])
 
+
 def gen_filename(options, ext=None, now=None):
     if ext is None:
         if options.full:
@@ -412,10 +419,11 @@ def gen_filename(options, ext=None, now=None):
 # files, from the time of the most recent full backup preceding
 # options.date, up to options.date.
 
-import re
+
 is_data_file = re.compile(r'\d{4}(?:-\d\d){5}\.(?:delta)?fsz?$').match
 del re
 
+
 def find_files(options):
     when = options.date
     if not when:
@@ -455,10 +463,11 @@ def find_files(options):
 #
 #     None, None, None, None
 
+
 def scandat(repofiles):
     fullfile = repofiles[0]
     datfile = os.path.splitext(fullfile)[0] + '.dat'
-    fn = startpos = endpos = sum = None # assume .dat file missing or empty
+    fn = startpos = endpos = sum = None  # assume .dat file missing or empty
     try:
         fp = open(datfile)
     except IOError as e:
@@ -475,6 +484,7 @@ def scandat(repofiles):
 
     return fn, startpos, endpos, sum
 
+
 def delete_old_backups(options):
     # Delete all full backup files except for the most recent full backup file
     all = sorted(filter(is_data_file, os.listdir(options.repository)))
@@ -515,6 +525,7 @@ def delete_old_backups(options):
             pass
         os.unlink(os.path.join(options.repository, fname))
 
+
 def do_full_backup(options):
     options.full = True
     tnow = gen_filedate(options)
@@ -714,7 +725,8 @@ def do_recover(options):
                         "%s has checksum %s instead of %s" % (
                             repofile, reposum, expected_truth['sum']))
                 totalsz += reposz
-                log("Recovered chunk %s : %s bytes, md5: %s", repofile, reposz, reposum)
+                log("Recovered chunk %s : %s bytes, md5: %s",
+                    repofile, reposz, reposum)
             log("Recovered a total of %s bytes", totalsz)
         else:
             reposz, reposum = concat(repofiles, outfp)
@@ -725,7 +737,8 @@ def do_recover(options):
             source_index = '%s.index' % last_base
             target_index = '%s.index' % options.output
             if os.path.exists(source_index):
-                log('Restoring index file %s to %s', source_index, target_index)
+                log('Restoring index file %s to %s',
+                    source_index, target_index)
                 shutil.copyfile(source_index, target_index)
             else:
                 log('No index file to restore: %s', source_index)
@@ -737,8 +750,8 @@ def do_recover(options):
         try:
             os.rename(temporary_output_file, options.output)
         except OSError:
-            log("ZODB has been fully recovered as %s, but it cannot be renamed into : %s",
-                temporary_output_file, options.output)
+            log("ZODB has been fully recovered as %s, but it cannot be renamed"
+                " into : %s", temporary_output_file, options.output)
             raise
 
 
@@ -759,10 +772,12 @@ def do_verify(options):
             log("Verifying %s", filename)
             try:
                 if filename.endswith('fsz'):
-                    actual_sum, size = get_checksum_and_size_of_gzipped_file(filename, options.quick)
+                    actual_sum, size = get_checksum_and_size_of_gzipped_file(
+                        filename, options.quick)
                     when_uncompressed = ' (when uncompressed)'
                 else:
-                    actual_sum, size = get_checksum_and_size_of_file(filename, options.quick)
+                    actual_sum, size = get_checksum_and_size_of_file(
+                        filename, options.quick)
                     when_uncompressed = ''
             except IOError:
                 error("%s is missing", filename)

src/ZODB/scripts/space.py

@@ -12,6 +12,7 @@ from ZODB.FileStorage import FileStorage
 from ZODB.utils import U64, get_pickle_metadata, load_current
 import six
 
+
 def run(path, v=0):
     fs = FileStorage(path, read_only=1)
     # break into the file implementation
@@ -31,12 +32,13 @@ def run(path, v=0):
         if v:
             print("%8s %5d %s" % (U64(oid), len(data), key))
     L = totals.items()
-    L.sort(lambda a, b: cmp(a[1], b[1]))
+    L.sort(key=lambda x: x[1])
     L.reverse()
     print("Totals per object class:")
     for key, (bytes, count) in L:
         print("%8d %8d %s" % (count, bytes, key))
 
+
 def main():
     import sys
     import getopt
@@ -56,5 +58,6 @@ def main():
     path = args[0]
     run(path, v)
 
+
 if __name__ == "__main__":
     main()

src/ZODB/scripts/tests/test_doc.py

@@ -38,6 +38,7 @@ checker = zope.testing.renormalizing.RENormalizing([
      "length=<LENGTH> offset=4 (+48)"),
 ])
 
+
 def test_suite():
     return unittest.TestSuite((
         doctest.DocFileSuite(
@@ -45,4 +46,4 @@ def test_suite():
             'fstail.txt',
             setUp=ZODB.tests.util.setUp, tearDown=ZODB.tests.util.tearDown,
             checker=checker),
-        ))
+    ))

src/ZODB/scripts/tests/test_fsdump_fsstats.py

@@ -57,6 +57,3 @@ class FsdumpFsstatsTests(TestCase):
         with open("stdout") as f:
             self.assertEqual(f.readline().strip(),
                              "Summary: 1 txns, 1 objects, 1 revisions")
-        
-                    
-                    

src/ZODB/scripts/tests/test_fstest.py

@@ -19,6 +19,7 @@ import ZODB
 from zope.testing import setupstack
 from zope.testing.renormalizing import RENormalizing
 
+
 def test_fstest_verbose():
     r"""
     >>> db = ZODB.DB('data.fs')
@@ -52,4 +53,3 @@ def test_suite():
         doctest.DocTestSuite(setUp=setupstack.setUpDirectory,
                              tearDown=setupstack.tearDown),
     ])
-

src/ZODB/tests/Corruption.py

@@ -23,6 +23,7 @@ from ZODB.utils import load_current
 
 from .StorageTestBase import StorageTestBase
 
+
 class FileStorageCorruptTests(StorageTestBase):
 
     def setUp(self):

src/ZODB/tests/HistoryStorage.py

@@ -21,6 +21,7 @@ import sys
 from time import time, sleep
 from ZODB.tests.MinPO import MinPO
 
+
 class HistoryStorage(object):
     def checkSimpleHistory(self):
         self._checkHistory((11, 12, 13))
@@ -29,7 +30,7 @@ class HistoryStorage(object):
         start = time()
         # Store a couple of revisions of the object
         oid = self._storage.new_oid()
-        self.assertRaises(KeyError,self._storage.history,oid)
+        self.assertRaises(KeyError, self._storage.history, oid)
         revids = [None]
         for data in data:
             if sys.platform == 'win32':

src/ZODB/tests/MVCCMappingStorage.py

@@ -110,7 +110,7 @@ class MVCCMappingStorage(MappingStorage):
         self._polled_tid = self._ltid = new_tid
         return list(changed_oids)
 
-    def tpc_finish(self, transaction, func = lambda tid: None):
+    def tpc_finish(self, transaction, func=lambda tid: None):
         self._data_snapshot = None
         with self._main_lock:
             return MappingStorage.tpc_finish(self, transaction, func)