bpo-30977: make uuid.UUID use __slots__ (GH-9078)

Co-Authored-By: Wouter Bolsterlee.

Lib/test/test_uuid.py

@@ -4,8 +4,10 @@ import builtins
 import contextlib
 import io
 import os
+import pickle
 import shutil
 import subprocess
+import sys
 
 py_uuid = support.import_fresh_module('uuid', blocked=['_uuid'])
 c_uuid = support.import_fresh_module('uuid', fresh=['_uuid'])
@@ -311,6 +313,64 @@ class BaseTestUUID:
         node2 = self.uuid.getnode()
         self.assertEqual(node1, node2, '%012x != %012x' % (node1, node2))
 
+    def _setup_for_pickle(self):
+        orig_uuid = sys.modules.get('uuid')
+        sys.modules['uuid'] = self.uuid
+
+        def restore_uuid_module():
+            if orig_uuid is not None:
+                sys.modules['uuid'] = orig_uuid
+            else:
+                del sys.modules['uuid']
+        self.addCleanup(restore_uuid_module)
+
+    def test_pickle_roundtrip(self):
+        self._setup_for_pickle()
+
+        u = self.uuid.UUID('12345678123456781234567812345678')
+        self.assertEqual(u, pickle.loads(pickle.dumps(u)))
+
+    def test_unpickle_previous_python_versions(self):
+        self._setup_for_pickle()
+
+        u = self.uuid.UUID('12345678123456781234567812345678')
+
+        # Python 2.7 protocol 0-2 pickles of u
+        py27_pickles = [
+            b'ccopy_reg\n_reconstructor\np0\n(cuuid\nUUID\np1\nc__builtin__\nob'
+            b'ject\np2\nNtp3\nRp4\n(dp5\nS\'int\'\np6\nL24197857161011715162171'
+            b'839636988778104L\nsb.',
+            b'ccopy_reg\n_reconstructor\nq\x00(cuuid\nUUID\nq\x01c__builtin__\n'
+            b'object\nq\x02Ntq\x03Rq\x04}q\x05U\x03intq\x06L2419785716101171516'
+            b'2171839636988778104L\nsb.',
+            b'\x80\x02cuuid\nUUID\nq\x00)\x81q\x01}q\x02U\x03intq\x03\x8a\x10xV'
+            b'4\x12xV4\x12xV4\x12xV4\x12sb.',
+        ]
+        # Python 3.6 protocol 0-4 pickles of u
+        py36_pickles = [
+            b'ccopy_reg\n_reconstructor\np0\n(cuuid\nUUID\np1\nc__builtin__\nob'
+            b'ject\np2\nNtp3\nRp4\n(dp5\nVint\np6\nL241978571610117151621718396'
+            b'36988778104L\nsb.',
+            b'ccopy_reg\n_reconstructor\nq\x00(cuuid\nUUID\nq\x01c__builtin__\n'
+            b'object\nq\x02Ntq\x03Rq\x04}q\x05X\x03\x00\x00\x00intq\x06L2419785'
+            b'7161011715162171839636988778104L\nsb.',
+            b'\x80\x02cuuid\nUUID\nq\x00)\x81q\x01}q\x02X\x03\x00\x00\x00intq'
+            b'\x03\x8a\x10xV4\x12xV4\x12xV4\x12xV4\x12sb.',
+            b'\x80\x03cuuid\nUUID\nq\x00)\x81q\x01}q\x02X\x03\x00\x00\x00intq'
+            b'\x03\x8a\x10xV4\x12xV4\x12xV4\x12xV4\x12sb.',
+            b'\x80\x04\x950\x00\x00\x00\x00\x00\x00\x00\x8c\x04uuid\x94\x8c\x04'
+            b'UUID\x94\x93\x94)\x81\x94}\x94\x8c\x03int\x94\x8a\x10xV4\x12xV4'
+            b'\x12xV4\x12xV4\x12sb.',
+        ]
+
+        for pickled in py27_pickles + py36_pickles:
+            unpickled = pickle.loads(pickled)
+            self.assertEqual(unpickled, u)
+            # is_safe was added in 3.7.  When unpickling values from older
+            # versions, is_safe will be missing, so it should be set to
+            # SafeUUID.unknown.
+            self.assertEqual(unpickled.is_safe, self.uuid.SafeUUID.unknown)
+
     # bpo-32502: UUID1 requires a 48-bit identifier, but hardware identifiers
     # need not necessarily be 48 bits (e.g., EUI-64).
     def test_uuid1_eui64(self):

Lib/uuid.py

@@ -118,6 +118,8 @@ class UUID:
                     uuid_generate_time_safe(3).
     """
 
+    __slots__ = ('int', 'is_safe')
+
     def __init__(self, hex=None, bytes=None, bytes_le=None, fields=None,
                        int=None, version=None,
                        *, is_safe=SafeUUID.unknown):
@@ -201,8 +203,30 @@ class UUID:
             # Set the version number.
             int &= ~(0xf000 << 64)
             int |= version << 76
-        self.__dict__['int'] = int
-        self.__dict__['is_safe'] = is_safe
+        object.__setattr__(self, 'int', int)
+        object.__setattr__(self, 'is_safe', is_safe)
+
+    def __getstate__(self):
+        d = {attr: getattr(self, attr) for attr in self.__slots__}
+        # is_safe is a SafeUUID instance.  Return just its value, so that
+        # it can be unpickled in older Python versions without SafeUUID.
+        d['is_safe'] = d['is_safe'].value
+        return d
+
+    def __setstate__(self, state):
+        # is_safe was added in 3.7
+        state.setdefault('is_safe', SafeUUID.unknown.value)
+
+        for attr in self.__slots__:
+            value = state[attr]
+
+            # for is_safe, restore the SafeUUID from the stored value
+            if attr == 'is_safe':
+                try:
+                    value = SafeUUID(value)
+                except ValueError:
+                    value = SafeUUID.unknown
+            object.__setattr__(self, attr, value)
 
     def __eq__(self, other):
         if isinstance(other, UUID):

Misc/NEWS.d/next/Library/2018-09-06-10-07-46.bpo-30977.bP661V.rst

+Make uuid.UUID use ``__slots__`` to reduce its memory footprint. Based on
+original patch by Wouter Bolsterlee.