Use ZERO_TID instead of None.

There is no strong reason to use None, and it makes code more complex.

git-svn-id: https://svn.erp5.org/repos/neo/trunk@2477 71dcc9de-d417-0410-9af5-da40c76e7ee4

neo/master/transactions.py

@@ -17,6 +17,7 @@
 
 from time import time, gmtime
 from struct import pack, unpack
+from neo.protocol import ZERO_TID
 from datetime import timedelta, datetime
 from neo.util import dump
 import neo
@@ -175,13 +176,13 @@ class TransactionManager(object):
     """
         Manage current transactions
     """
+    _last_tid = ZERO_TID
 
     def __init__(self):
         # tid -> transaction
         self._tid_dict = {}
         # node -> transactions mapping
         self._node_dict = {}
-        self._last_tid = None
         self._last_oid = None
 
     def __getitem__(self, tid):
@@ -234,7 +235,7 @@ class TransactionManager(object):
                 gmt.tm_min),
             int((gmt.tm_sec % 60 + (tm - int(tm))) / SECOND_PER_TID_LOW)
         ))
-        if self._last_tid is not None and tid <= self._last_tid:
+        if tid <= self._last_tid:
             tid  = addTID(self._last_tid, 1)
         self._last_tid = tid
         return self._last_tid
@@ -249,10 +250,7 @@ class TransactionManager(object):
         """
             Set the last TID, keep the previous if lower
         """
-        if self._last_tid is None:
-            self._last_tid = tid
-        else:
-            self._last_tid = max(self._last_tid, tid)
+        self._last_tid = max(self._last_tid, tid)
 
     def reset(self):
         """

neo/tests/master/testTransactions.py

@@ -19,6 +19,7 @@ import unittest
 from mock import Mock
 from struct import pack, unpack
 from neo.tests import NeoUnitTestBase
+from neo.protocol import ZERO_TID
 
 from neo.master.transactions import Transaction, TransactionManager
 from neo.master.transactions import packTID, unpackTID, addTID
@@ -126,7 +127,7 @@ class testTransactionManager(NeoUnitTestBase):
     def test_getNextTID(self):
         txnman = TransactionManager()
         # no previous TID
-        self.assertEqual(txnman.getLastTID(), None)
+        self.assertEqual(txnman.getLastTID(), ZERO_TID)
         # first transaction
         node1 = Mock({'__hash__': 1})
         tid1 = txnman.begin()