Python：检查'Dictionary'是否为空似乎不起作用 [英] Python: Checking if a 'Dictionary' is empty doesn't seem to work

问题描述

我正在尝试检查一个字典是否为空，但是它的行为不正常。它只是跳过它，并显示在线，除了显示消息之外没有任何东西。任何想法为什么？

I am trying to check if a dictionary is empty but it doesn't behave properly. It just skips it and displays ONLINE without anything except of display the message. Any ideas why ?

 def isEmpty(self, dictionary):
   for element in dictionary:
     if element:
       return True
     return False

 def onMessage(self, socket, message):
  if self.isEmpty(self.users) == False:
     socket.send("Nobody is online, please use REGISTER command" \
                 " in order to register into the server")
  else:
     socket.send("ONLINE " + ' ' .join(self.users.keys())) 

推荐答案

空字典评估为 False在Python中 ：

>>> dct = {}
>>> bool(dct)
False
>>> not dct
True
>>>

因此，您的 isEmpty 函数是不必要的。所有你需要做的是：

Thus, your isEmpty function is unnecessary. All you need to do is:

def onMessage(self, socket, message):
    if not self.users:
        socket.send("Nobody is online, please use REGISTER command" \
                    " in order to register into the server")
    else:
        socket.send("ONLINE " + ' ' .join(self.users.keys()))

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