python空值判断方式(if xxx和if xxx is None的区别及说明)_python

if __name__ == '__main__':
    print("---not None == (not '') == (not 0) == (not []) == (not {}) == (not ()) == (not False)---")
    print(not None == (not '') == (not 0) == (not []) == (not {}) == (not ()) == (not False))

if __name__ == '__main__':
    print("---output a,b---")
    a = []
    b = None
    print("a=[]")
    print("b=None")
    print("--- if x")
    if a:
        print("a")
    else:
        print("None")
    if b:
        print("b")
    else:
        print("None")

if __name__ == '__main__':
    a = []
    b = None
    print("a=[]")
    print("b=None")
    print("--- is None")
    if a is None:
        print("None")
    else:
        print("a")
    if b is None:
        print("None")
    else:
        print("b")

if __name__ == '__main__':
    print("---not None == (not '') == (not 0) == (not []) == (not {}) == (not ()) == (not False)---")
    print(not None == (not '') == (not 0) == (not []) == (not {}) == (not ()) == (not False))

    print("---output a,b---")
    a = []
    b = None
    print("a=[]")
    print("b=None")
    print("--- if x")
    if a:
        print("a")
    else:
        print("None")
    if b:
        print("b")
    else:
        print("None")

    print("--- is None")
    if a is None:
        print("None")
    else:
        print("a")
    if b is None:
        print("None")
    else:
        print("b")

    print("--- not")
    if not a:
        print("None")
    else:
        print("a")

    if not b:
        print("None")
    else:
        print("b")

    print("--- is not None")
    if a is not None:
        print("a")
    else:
        print("None")

    if b is not None:
        print("B")
    else:
        print("None")