python nonlocal的用法详解

count = 1 # 这里是声明的是全局变量，对于nonlocal来说全局变量是不包括的

def a():
    count = 'a函数里面' # 这里对于nonlocal来说就是外面的函数已声明的变量
    def b():
        nonlocal count # nonlocal count指的是函数b内
        print(count)
        count = 2
    b()
    print(count)

if __name__ == '__main__':
    a()
    print(count)

count = 1

def a():
    # count = 'a函数里面' # SyntaxError: no binding for nonlocal 'count' found
    def b():
        nonlocal count
        print(count)
        count = 2
    b()
    print(count)

if __name__ == '__main__':
    a()
    print(count)

count = 1

def a():
    count = 'a函数里面'
    def b():
        count = 2
        print(count)
        def c():
            nonlocal count
            print(count)
        c()
    b()
    print(count)

if __name__ == '__main__':
    a()
    print(count)

def scope_test():
    def do_local():
        spam = "local spam"

    def do_nonlocal():
        nonlocal spam
        spam = "nonlocal spam"

    def do_global():
        global spam
        spam = "global spam"

    spam = "test spam"
    do_local()
    print("After local assignment:", spam)
    do_nonlocal()
    print("After nonlocal assignment:", spam)
    do_global()
    print("After global assignment:", spam)

scope_test()
print("In global scope:", spam)