如何在此场景中使用global？

Question

我是个编程新手，我真的不明白如何使用很多这样的代码。如果有人告诉我在这种情况下如何使用global，会对我有很大的帮助。

def tshirtadd():
    global perch
    perch = 0
    print("you have",perch,"T-shirts")
    add = int(input("how many t-shirts would you like to add? "))
    perch+add
    return perch


def tshirtremove():
    global perch
    print("You have",perch,"Tshirts")
    remove = int(input("How many Tshirts would you like to remove? "))

    perch - remove

    return perch


def order():
    global perch
    print(perch)
    print(perch*10)
    return main


def main():
    ordering = int(input("Would you like to add,remove, view order, or purchase?"))
    print(list1)
    count = 0
    for x in list1:
        count = count+1
        print(count,"\b)",x)
    perch = 0

    if ordering == 1:
        tshirtadd()
        print("you have",perch,"Tshirts")
        return main()
    elif ordering == 2:
        tshirtremove()
        return main()
    elif ordering == 3:
        order()
        return main()
    else:
        exit
    print(perch)
main()

Answer 1

您应该在使用global之前初始化变量perch，perch = 0应该在函数定义之前的顶部。

我认为您正在尝试初始化主函数中的perch，但这不是全局函数的工作方式，您需要在所有函数之前在外部定义它，并且您可以像其他函数一样在main()中使用全局perch，如果需要，可以在那里将其设置为零

Answer 2

回答你的问题:当我们想要从任何地方访问我们的变量时，我们通常使用global。所以你只需要定义一次global variable，你就可以在任何地方使用它。

我对你的代码做了一些修改。(需要更多更改，但不确定这段代码真正想要实现的是什么)

这可能会帮助您理解global的概念

def tshirtadd():

        print("you have",perch,"T-shirts")
        add = int(input("how many t-shirts would you like to add? "))
        perch += add
        return perch


    def tshirtremove():
        print("You have",perch,"Tshirts")
        remove = int(input("How many Tshirts would you like to remove? "))

        perch -= remove

        return perch


    def order():
        print(perch)
        print(perch*10)
        return main


    def main():
        global perch
        perch = 0
        ordering = int(input("Would you like to add,remove, view order, or purchase?"))
        print(list1)
        count = 0
        for x in list1:
            count = count+1
            print(count,"\b)",x)
        perch = 0

        if ordering == 1:
            tshirtadd()
            print("you have",perch,"Tshirts")
            return main()
        elif ordering == 2:
            tshirtremove()
            return main()
        elif ordering == 3:
            order()
            return main()
        else:
            exit
        print(perch)
    main()