python - 可能的全局变量问题？

Question

我正在做这个家庭作业，但我被困在一个我知道是一个非常简单的问题上。该代码的前提是一个小额现金系统，用户可以在其中存款、取款并获取当前余额。我的问题是提款和存款似乎没有通过我的帐户类。是全局变量的问题吗？稍后我将添加时间戳。预先感谢您。

import datetime
import time

class Account:
    def __init__(self, initial):
        self.balance = initial

    def deposit(self, amt):
        self.balance = self.balance + amt

    def withdraw(self,amt):
        self.balance = self.balance - amt

    def getbalance(self):
        return self.balance

def yesno(prompt): 
    ans = raw_input(prompt) 
    return (ans[0]=='y' or ans[0]=='Y')

def run():  
    done = 0   
    while not done: 
        user_options()
        print
        done = not yesno("Do another? ")
        print

def user_options():
    print ("Here are your options:")
    print
    print ("   (a) Deposit cash")
    print ("   (b) Withdraw cash")
    print ("   (c) Print Balance")
    print
    u = raw_input("Please select a letter option: ").lower()
    user_input(u)

def user_input(choice):
    account = Account(0.00)
    if choice == "a" or choice == "b" or choice == "c":

        if choice == "a":
            d = input("Enter Deposit Amount: $")
            account.deposit(d)

        if choice == "b":
            w = input ("Enter Withdraw Amount: $")
            account.withdraw(w)

        if choice == "c":
            print ("Balance Amount: $"),
            print account.getbalance()

    else:
        print ("Not a correct option")


run()

#now = datetime.datetime.now()

Python版本:2.7.2

Answer 1

问题是:

account = Account(0.00)

每次调用 user_input 时，您都会创建一个新的空帐户。由于 user_input 是从 user_options 调用的，而 user_options 在运行时的 while 循环内调用，因此这发生在每个事务之前。

您需要将该行移出循环，例如:

def run():
    done = 0
    global account # just showing you one way, not recommending this
    account = Account(0.00)
    while not done:
        user_options()
        print
        done = not yesno("Do another? ")
        print