通过python类外部的函数更改类中变量的值

Question

我正在尝试使用该类外部的函数来修改位于类内部的变量（在这种情况下为整数）的值。但是，当我调用该函数时，变量us_balance的值保持不变：42。

class Country:
    us_balance = 42

def buy(country, amount):
    if country.lower == "us":
        Country.us_balance = Country.us_balance - amount

def stats():
    print(Country.us_balance)

while True:
    user_input = input("> ").lower()

    if user_input == "buy":
        amount = input("$ ").lower()
        balance_to_set = amount.split()
        buy(balance_to_set[0], int(balance_to_set[1]))
    if user_input == "stats":
        stats()
        break

关于如何解决此问题的任何想法？

Answer 1

这是一个适合您的示例。

class Country:
    us_balance = 42

def buy(ci, country, amount):
    if country.lower() == "us":
        new = ci.us_balance = ci.us_balance - amount
        ci.us_balance = new

def stats(ci):
    print(ci.us_balance)

# Create an instance of the class
ci = Country()

while True:
    user_input = input("> ").lower()

    if user_input == "buy":
        amount = input("$ ").lower()
        balance_to_set = amount.split()
        buy(ci, balance_to_set[0], int(balance_to_set[1]))
    if user_input == "stats":
        stats(ci)
        break

Answer 2