python - 如果Python中输入无效，如何让程序再次提示？

Question

我需要再次询问选择，直到用户选择有效的选项。

choice = input('Please choose 1,2,3\n')

if choice == 1:
print('You have chosen the first option')

elif choice == 2:
print('You have chosen the second option')

elif choice == 3:
print('You have chosen the third option')

else:
print('This is not an option, please try again.')

Answer 1

也许我错了，因为我只是一个黑客，但我相信一个更“Pythonic”的答案是:

choices = {1:'first', 2:'second', 3:'third'}

while True:
    choice = input('Please choose 1, 2, or 3.\n')
    try:
        print 'You have chosen the {} option.'.format(choices[choice])
        break
    except KeyError:
        print 'This is not an option; please try again.'

或者至少:

while True:
    choice = input('Please choose 1, 2, or 3.\n')

    if choice == 1:
        print 'You have chosen the first option'
        break
    elif choice == 2:
        print 'You have chosen the second option'
        break
    elif choice == 3:
        print 'You have chosen the third option'
        break
    else:
        print 'This is not an option; please try again.'

这两者都避免创建不必要的测试变量，第一个减少了所需的总体代码。

对于 Python 3，我相信在打印语句周围添加括号应该是唯一的变化。该问题未标记版本。