Question

我很想知道是否需要在Python的顶级声明/赋值中使用关键字global（例如下面第一行代码中的关键字）。

fn_2()和fn_4()对改变以下代码中的相应变量具有相同的效果。

global factor_1
factor_1 = None

factor_2 = None

def main():

    print('factor_1 = {}, factor_2 = {}'.format(factor_1, factor_2))

    fn_1()
    print('factor_1 = {}, factor_2 = {}'.format(factor_1, factor_2))

    fn_2()
    print('factor_1 = {}, factor_2 = {}'.format(factor_1, factor_2))

    fn_3()
    print('factor_1 = {}, factor_2 = {}'.format(factor_1, factor_2))

    fn_4()
    print('factor_1 = {}, factor_2 = {}'.format(factor_1, factor_2))

def fn_1():
    factor_1 = 10

def fn_2():
    global factor_1
    factor_1 = 20

def fn_3():
    factor_2 = 30

def fn_4():
    global factor_2
    factor_2 = 40

if __name__ == '__main__':
    main()

Answer 1

不，没有。如果要在该函数中设置全局变量的值，则需要在函数内使用global。您不需要使用global外部功能。

Answer 2

global允许您使用超出函数范围的变量，因此必须在函数内部使用它：

def fn_1():
    # this is declaring a local variable factor_1
    factor_1 = 10

def fn_2():
    # this is changing the value of the global variable factor_1
    global factor_1
    factor_1 = 20

def fn_3():
    # this is declaring a local variable factor_2
    factor_2 = 30

def fn_4():
    # this is changing the value of the global variable factor_2
    global factor_2
    factor_2 = 40

＆＃34;全球＆＃34;顶级声明中需要的关键字

2 个答案: