python-3.x - 为什么我们将valid_input初始化为false并在这个python代码中使用'while not' valid_input

Question

def get_yes_or_no(message):
    valid_input = False
    while not valid_input:
        answer = input(message)
        answer = answer.upper() # convert to upper case
        if answer == 'Y' or answer == 'N':
            valid_input = True
        else:
            print('Please enter Y for yes or N for no.')
    return answer

Answer 1

甚至没有真正需要使用valid_input变量；你可以有一个无限循环return：

def get_yes_or_no(message):
    while True:
        answer = input(message).upper() # convert to upper case
        if answer == 'Y' or answer == 'N':
            return answer
        print('Please enter Y for yes or N for no.')