编写干净、灵活且易于维护的用户输入提示

我曾经为类似的东西写过一个函数。解释在文档字符串中：

def xory(question = "", setx = ["yes"], sety = ["no"], setz = [], strict = False):
    """xory([question][, setx][, sety][, setz][, strict]) -> string

    Asks question.  If the answer is equal to one of the elements in setx,
    returns True.  If the answer is equal to one of the elements in sety,
    returns False.  If the answer is equal to one of the elements in setz,
    returns the element in setz that answer is equal to.  If the answer is
    not in any of the sets, reasks the question.  Strict controls whether
    the answer is case-sensitive.  If show is True, an indication of the
    acceptable answers will be displayed next to the prompt."""

    if isinstance(setx, str):
        setx = [setx]
    if isinstance(sety, str):
        sety = [sety]
    if isinstance(setz, str):
        setz = [setz]
    if (setx[0])[0] != (sety[0])[0]:
        setx = [(setx[0])[0]] + setx
        sety = [(sety[0])[0]] + sety
    question = question.strip(" ") + " "
    while True:
        if show:
            shows = "[%s/%s] " % (setx[0], sety[0])
        else:
            shows = ""
        user_input = raw_input(question + shows)
        for y in [setx, sety, setz]:
            for x in y:
                if (user_input == x) or ((not strict) and (user_input.lower() == x.lower())):
                    if y is setx:
                        return True
                    elif y is sety:
                        return False
                    else:
                        return x
        question = ""
        show = True

例子：

>>> response = xory("1 or 0?", ["1", "one", "uno"], ["0", "zero", "null"], ["quit", "exit"])
1 or 0? x
[1/0] eante
[1/0] uno
>>> print(response)
True
>>> response = xory("Is that so?")
Is that so? Who knows?
[y/n] no
>>> print(response)
False
>>> response = xory("Will you do it?", setz=["quit", "exit", "restart"])
Will you do it? hm
[y/n] quit
>>> print(response)
quit

我建议编写一个包含许多定义非常明确的构建块的库，每个构建块都尽可能小巧轻便，不要对如何将这些组件组合在一起进行太多假设。

也就是说，我将包含一个执行循环的函数，但不是传入一组规则，而是只允许传入一个函数，该函数要么返回一个值（如果给定了有效的输入，并且在以任何必要的方式转换它之后）或在输入不可用时引发一个值。其他构建块将实现某些检查或转换（例如布尔值的解析和转换为布尔值）。ValueError'y''n'

这样，您将完全由用户以适合用例的方式组装东西。

# library:

def prompt(prompt, default, postprocess):
    value = input('{} ({}): '.format(prompt, default)) or default
    try:
        return postprocess(value)
    except ValueError:
        continue

def check_lower(value):
    if not value.islower():
        raise ValueError()

def to_bool(value):
    return value in 'yes'

# using the library:

def postprocess(value):
    check_lower(value)
    return to_bool(value)

prompt('Really?', 'n', postprocess)

我会创建一个提示函数，如下所示：

def prompt(prompt, default=None, rules=[]):
    while True:
        response = input(prompt)
        if response:
            valid = [rule(response) for rule in rules]
            if not(False in valid):
                return response
            else:
                print('Invalid input')
        else:
            return default

然后，您可以创建不同的验证函数，例如

def filterValidEmail(string):
    if '@' in string:
        if '.' in string.split('@')[1]:
            return True
        else:
            return False
    else:
        return False

并像这样调用这些函数：

prompt('What is your email? ', rules=[filterValidEmail])

您还可以对此进行调整，以便可以告诉用户他们失败了什么验证或不允许空白输入。