Question

在此代码中

money = .3

Things = ["Nothing"]

def main():
    print "go to buy things"
    print "Current Money %s" % (money)
    print "Things you have:"
    for item in Things:
        print item
    wait = raw_input()
    buythings(money)


def buythings(money):
    print "Type Buy to buy things"
    buy = raw_input()
    if buy == "buy":
        money = money - .3
        Things.append("Things")
        main()
    else:
        print "you bought nothing"
        print ""
        main()

为什么买东西后钱不会下降？这对我来说已经有一段时间了，我似乎无法理解范围在这种情况下是如何工作的。

Answer 1

全局变量money被money函数中的函数参数buythings(money)遮蔽。您应该删除它的参数：

def main():
    global money
    global Things
    ...

def buythings():
    global money
    global Things
    ...

然而，正如alfasin指出的那样，更好的方法是将money和Things作为参数传递给两个函数，而不是使用global关键字：< / p>

def main(money, things):
    ...
    for item in things:
        print item
    wait = raw_input()
    buythings(money, things)


def buythings(money, things):
    ...
    if buy == "buy":
        money = money - .3
        Things.append("Things")
        main(money, things)
    else:
        ...
        main(money, things)

>>> money = .3
>>> Things = ["Nothing"]
>>> main(money, Things)

希望这有帮助。

Answer 2

您可以在其他函数中使用全局变量，方法是在分配给它的每个函数中将其声明为全局变量：

money = 0

def set_money_to_one():
    global money    # Needed to modify global copy of money
    money = 1

def print_money():
    print money     # No need for global declaration to read value of money

set_money_to_one()
print_money()       # Prints 1

在你的情况下：

def buythings():
    global money

Python希望确保你真正知道自己是什么通过明确要求全局关键字来玩。

全局范围变量在python中不变

2 个答案: