Python错误：为什么python无法识别我对象的类型？

Question

class Network():
    tables = []
def readInFile():
    network = Network()
def printThing(network):
    print(len(network.tables))
def main():
    network = readInFile()
    printThing(network)
if __name__ == "__main__":
    main()

gives error: File "thing.py", line 6, in printThing print(len(network.tables)) AttributeError: 'NoneType' object has no attribute 'tables'

But the object network isn't NoneType it's clearly of type Network() when it is instantiated in the readInFile function, and type Network() has the attribute tables! Please help, thanks

Answer 1

You need to return something from your function. Unless your function has a return statement in it, it will return None

class Network():
    tables = []

def readInFile():
    return Network()

def printThing(network):
    print(len(network.tables))

def main():
    network = readInFile()
    printThing(network)

if __name__ == "__main__":
    main()

Answer 2

您的函数readInFile（）没有return语句，因此始终返回None。