Clean up py/vtdb class variables.

Remove class variables that shadow object variables. These are a
potential source of hard-to-find bugs. Move initial values into object
__init__ methods instead.

py/vtdb/cursor.py

@@ -6,16 +6,15 @@ from vtdb import dbexceptions
 
 
 class BaseCursor(object):
-  arraysize = 1
-  lastrowid = None
-  rowcount = 0
-  results = None
-  connection = None
-  description = None
-  index = None
 
   def __init__(self, connection):
     self.connection = connection
+    self.arraysize = 1
+    self.lastrowid = None
+    self.rowcount = 0
+    self.results = None
+    self.description = None
+    self.index = None
 
   def close(self):
     self.connection = None
@@ -139,15 +138,14 @@ class BatchQueryItem(object):
 
 
 class StreamCursor(object):
-  arraysize = 1
-  conversions = None
-  connection = None
-  description = None
-  index = None
-  fetchmany_done = False
 
   def __init__(self, connection):
     self.connection = connection
+    self.arraysize = 1
+    self.conversions = None
+    self.description = None
+    self.index = None
+    self.fetchmany_done = False
 
   def close(self):
     self.connection = None

py/vtdb/cursorv3.py

@@ -2,23 +2,20 @@
 # Use of this source code is governed by a BSD-style license that can
 # be found in the LICENSE file.
 
-from vtdb import cursor
 from vtdb import dbexceptions
 
 
 class Cursor(object):
-  _conn = None
-  tablet_type = None
-  arraysize = 1
-  lastrowid = None
-  rowcount = 0
-  results = None
-  description = None
-  index = None
 
   def __init__(self, connection, tablet_type):
     self._conn = connection
     self.tablet_type = tablet_type
+    self.arraysize = 1
+    self.lastrowid = None
+    self.rowcount = 0
+    self.results = None
+    self.description = None
+    self.index = None
 
   def close(self):
     self.results = None
@@ -111,12 +108,10 @@ class Cursor(object):
 
 
 class StreamCursor(Cursor):
-  arraysize = 1
-  conversions = None
-  connection = None
-  description = None
-  index = None
-  fetchmany_done = False
+
+  def __init__(self, connection, tablet_type):
+    super(StreamCursor, self).__init__(connection, tablet_type)
+    self.fetchmany_done = False
 
   def execute(self, sql, bind_variables, **kargs):
     self.description = None

py/vtdb/keyspace.py

@@ -16,11 +16,6 @@ class Keyspace(object):
 
   Provide functions to extract sharding information from the same.
   """
-  name = None
-  partitions = None
-  sharding_col_name = None
-  sharding_col_type = None
-  served_from = None
 
   # load this object from a SrvKeyspace object generated by vt
   def __init__(self, name, data):

py/vtdb/tablet.py

@@ -67,16 +67,16 @@ class TabletConnection(object):
   If something goes wrong, this object should be thrown away and a new
   one instantiated.
   """
-  transaction_id = 0
-  session_id = 0
-  _stream_fields = None
-  _stream_conversions = None
-  _stream_result = None
-  _stream_result_index = None
 
   def __init__(
       self, addr, tablet_type, keyspace, shard, timeout, user=None,
       password=None, keyfile=None, certfile=None, caller_id=None):
+    self.transaction_id = 0
+    self.session_id = 0
+    self._stream_fields = None
+    self._stream_conversions = None
+    self._stream_result = None
+    self._stream_result_index = None
     self.addr = addr
     self.tablet_type = tablet_type
     self.keyspace = keyspace

py/vtdb/topo_utils.py

@@ -10,13 +10,6 @@ from zk import zkocc
 
 
 class VTConnParams(object):
-  keyspace = None
-  shard = None
-  db_type = None
-  addr = None
-  timeout = 0
-  user = None
-  password = None
 
   def __init__(self, keyspace_name, shard, db_type, addr, timeout,
                user, password):

py/vtdb/vtgatev3.py

@@ -88,14 +88,14 @@ def _create_req(sql, new_binds, tablet_type, not_in_transaction):
 
 class VTGateConnection(object):
   """This utilizes the V3 API of VTGate."""
-  session = None
-  _stream_fields = None
-  _stream_conversions = None
-  _stream_result = None
-  _stream_result_index = None
 
   def __init__(self, addr, timeout, user=None, password=None,
                keyfile=None, certfile=None):
+    self._stream_fields = None
+    self._stream_conversions = None
+    self._stream_result = None
+    self._stream_result_index = None
+    self.session = None
     self.addr = addr
     self.timeout = timeout
     self.client = bsonrpc.BsonRpcClient(addr, timeout, user, password,