比如
class TEST():
class_attr #类属性，通过TEST.class_attr调用，如果用instance.class_attr调用实际上是声明类另一个实例属性，与之前的TEST.class_attr不是一个东西了
def __init__(self,other):
self.class_attr #实例属性，与之前的那个属性处于不同的名字空间了，不是一个东西。
self.other=other
总之，__init__可以用来声明实例属性，以及进行必要的初始化。
#----------------------------------------------------------------------
# Copyright (c) 1999-2001, Digital Creations, Fredericksburg, VA, USA
# and Andrew Kuchling. All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met:
#
# o Redistributions of source code must retain the above copyright
# notice, this list of conditions, and the disclaimer that follows.
#
# o Redistributions in binary form must reproduce the above copyright
# notice, this list of conditions, and the following disclaimer in
# the documentation and/or other materials provided with the
# distribution.
#
# o Neither the name of Digital Creations nor the names of its
# contributors may be used to endorse or promote products derived
# from this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY DIGITAL CREATIONS AND CONTRIBUTORS *AS
# IS* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
# TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL DIGITAL
# CREATIONS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
# OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
# TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
# USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
# DAMAGE.
#----------------------------------------------------------------------
"""Support for Berkeley DB 4.3 through 5.3 with a simple interface.
For the full featured object oriented interface use the bsddb.db module
instead. It mirrors the Oracle Berkeley DB C API.
"""
import sys
absolute_import = (sys.version_info[0] >= 3)
if (sys.version_info >= (2, 6)) and (sys.version_info < (3, 0)) :
import warnings
if sys.py3kwarning and (__name__ != 'bsddb3') :
warnings.warnpy3k("in 3.x, the bsddb module has been removed; "
"please use the pybsddb project instead",
DeprecationWarning, 2)
warnings.filterwarnings("ignore", ".*CObject.*", DeprecationWarning,
"bsddb.__init__")
try:
if __name__ == 'bsddb3':
# import _pybsddb binary as it should be the more recent version from
# a standalone pybsddb addon package than the version included with
# python as bsddb._bsddb.
if absolute_import :
# Because this syntaxis is not valid before Python 2.5
exec("from . import _pybsddb")
else :
import _pybsddb
_bsddb = _pybsddb
from bsddb3.dbutils import DeadlockWrap as _DeadlockWrap
else:
import _bsddb
from bsddb.dbutils import DeadlockWrap as _DeadlockWrap
except ImportError:
# Remove ourselves from sys.modules
import sys
del sys.modules[__name__]
raise
# bsddb3 calls it db, but provide _db for backwards compatibility
db = _db = _bsddb
__version__ = db.__version__
error = db.DBError # So bsddb.error will mean something...
#----------------------------------------------------------------------
import sys, os
from weakref import ref
if sys.version_info < (2, 6) :
import UserDict
MutableMapping = UserDict.DictMixin
else :
import collections
MutableMapping = collections.MutableMapping
class _iter_mixin(MutableMapping):
def _make_iter_cursor(self):
cur = _DeadlockWrap(self.db.cursor)
key = id(cur)
self._cursor_refs[key] = ref(cur, self._gen_cref_cleaner(key))
return cur
def _gen_cref_cleaner(self, key):
# use generate the function for the weakref callback here
# to ensure that we do not hold a strict reference to cur
# in the callback.
return lambda ref: self._cursor_refs.pop(key, None)
def __iter__(self):
self._kill_iteration = False
self._in_iter += 1
try:
try:
cur = self._make_iter_cursor()
# FIXME-20031102-greg: race condition. cursor could
# be closed by another thread before this call.
# since we're only returning keys, we call the cursor
# methods with flags=0, dlen=0, dofs=0
key = _DeadlockWrap(cur.first, 0,0,0)[0]
yield key
next = getattr(cur, "next")
while 1:
try:
key = _DeadlockWrap(next, 0,0,0)[0]
yield key
except _bsddb.DBCursorClosedError:
if self._kill_iteration:
raise RuntimeError('Database changed size '
'during iteration.')
cur = self._make_iter_cursor()
# FIXME-20031101-greg: race condition. cursor could
# be closed by another thread before this call.
_DeadlockWrap(cur.set, key,0,0,0)
next = getattr(cur, "next")
except _bsddb.DBNotFoundError:
pass
except _bsddb.DBCursorClosedError:
# the database was modified during iteration. abort.
pass
# When Python 2.4 not supported in bsddb3, we can change this to "finally"
except :
