由于错误往往作为异常传递，因此成功/失败返回值很少有用，因此许多对象修饰符函数最终根本没有返回值，或者更准确地说，返回None，因为你不能什么都不返回。 （考虑一些 Python 的内置对象，例如list, where append and extend return None, and dict, where dict.update回报None.)
还是归来self对于链接方法调用来说很方便，即使有些 Python 爱好者不喜欢它。请参阅 kindall 的回答内部类方法应该返回值还是只修改Python中的实例变量？例如。
编辑以根据评论添加一些示例：
您“应该”返回什么（或引发异常，在这种情况下，“什么异常”）取决于问题。你想要send_message()等待响应、验证该响应并验证其是否良好？如果是这样，您是否希望它在没有响应、验证失败或响应有效但显示“消息被拒绝”时引发错误？如果是这样，你想要吗不同的每次失败的错误等？一种合理的（对于某些合理的值）方法是捕获具有“基本”异常的所有故障，并使每种“类型”的故障都是其派生：
class ZorgError(Exception): # catch-all "can't talk via the Zorg-brand XML API"
pass
class ZorgRemoteDown(ZorgError): # connect or send failed, or no response/timeout
pass
class ZorgNuts(ZorgError): # remote response incomprehensible
pass
class ZorgDenied(ZorgError): # remote says "permission denied"
pass
# add more if needed
现在你的一些函数可能看起来像这样（注意，这些都没有经过测试）：
def connect(self):
"""connect to server, log in"""
... # do some prep work
addr = self._addr
try:
self._sock.connect(addr)
except socket.error as err:
if err.errno == errno.ECONNREFUSED: # server is down
raise ZorgRemoteDown(addr) # translate that to our Zorg error
# add more special translation here if needed
raise # some other problem, propagate it
... # do other stuff now that we're connected, including trying to log in
response = self._get_response()
if response == 'login denied' # or whatever that looks like
raise ZorgDenied() # maybe say what exactly was denied, maybe not
# all went well, return None by not returning anything
def send_message(self, msg):
"""encode the message in the way the remote likes, send it, and wait for
a response from the remote."""
response = self._send_and_wait(self._encode(msg))
if response == 'ok':
return
if response == 'permission denied':
raise ZorgDenied()
# don't understand what we got back, so say the remote is crazy
raise ZorgNuts(response)
然后你需要一些“内部”函数，如下所示：
def _send_and_wait(self, raw_xml):
"""send raw XML to server"""
try:
self._sock.sendall(raw_xml)
except socket.error as err:
if err.errno in (errno.EHOSTDOWN, errno.ENETDOWN) # add more if needed
raise ZorgRemoteDown(self._addr)
raise
return self._get_response()
def _get_response(self):
"""wait for a response, which is supposedly XML-encoded"""
... some code here ...
if we_got_a_timeout_while_waiting:
raise ZorgRemoteDown(self._addr)
try:
return some_xml_decoding_stuff(raw_xml)
except SomeXMLDecodeError:
raise ZorgNuts(raw_xml) # or something else suitable for debug
您可以选择不翻译socket.error根本没有，并且没有所有错误都是你自己的；也许你可以把你的错误压缩成ValueError and KeyError等等。
这些选择就是编程的全部内容！
