Question

我正在尝试学习python，目前我正在尝试构建一个票务机，在这种情况下模拟付款步骤。因为它是用于演示目的的模拟，我要求用户通过布尔输入来输入True或false。出于某种原因，当我输入False时，它仍将被解释为True。以下是我的代码：

def payment():
    global tries
    print("Payment can be done by PIN. Please follow the instructions on the payment terminal\n")
    time.sleep(2)
    payment_succeeded = bool(input("for demonstration purpose: did the payment succeed?"))
    if payment_succeeded is True:
        print("Payment succeeded.\n")
        trip_time()
        time.sleep(1)
    elif tries < 3:
        tries +=1
        print("Payment Failed. please try again\n")
        time.sleep(0.5)
        payment()
    else:
        print("Payment has failed. Stopping purchase.\n")

全局“尝试”变量默认值为1

Answer 1

bool()未将'False'翻译为False。它只查看字符串的truth value，只有空字符串被视为false。

因此，输入除空字符串以外的任何内容被视为 true ：

>>> bool(input(''))
Howdy!
True
>>> bool(input(''))  # Hitting enter results in an empty string

False

你最好测试某些字符串：

response = input("for demonstration purpose: did the payment succeed?")
payment_succeeded = response.lower() in ('y', 'yes', 'it did', 'true', 'you betcha')
if payment_succeeded:   # no need for "is True" here

现在输入除预期字符串之外的任何内容都会导致payment_succeeded设置为False。

您可能希望通过提供预期输入来限制更多，并重新询问是否未给出：

while True:
    response = input("for demonstration purpose: did the payment succeed, yes or no?").lower()
    if response in ('y', 'yes', 'n', 'no'):
        payment_succeeded = response in ('y', 'yes')
        break
    print('Sorry, I did not understand that input, please try again.')

如果陈述总是如此

1 个答案: