Python：检查'Dictionary'是否为空似乎不起作用

Question

我正在试着检查字典是否是空的，但它的行为不正常。它只是跳过它并在线显示，除了显示消息之外没有任何东西。知道为什么吗？

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()))    

Answer 1

dict = {}
print(len(dict.keys()))

如果length为零，则表示dict为空

Answer 2

这里有三种方法可以检查dict是否为空。不过我更喜欢用第一种方式。另外两种方式都太罗嗦了。

test_dict = {}

if not test_dict:
    print "Dict is Empty"


if not bool(test_dict):
    print "Dict is Empty"


if len(test_dict) == 0:
    print "Dict is Empty"

Answer 3

空字典在Python中的计算结果为false:

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

因此，您的isempty函数是不必要的。你所需要做的就是：

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()))