从两个选择中选择一个强制性参数的Python函数 [英] Python function that takes one compulsory argument from two choices

问题描述

我有一个功能:

def delete(title=None, pageid=None):
    # Deletes the page given, either by its title or ID
    ...
    pass

但是，我的意图是让函数仅接受一个参数(title或pageid).例如，delete(title="MyPage")或delete(pageid=53342)有效，而delete(title="MyPage", pageid=53342)无效.不能传递零参数.我将如何去做?

However, my intention is for the function to take only one argument (either title OR pageid). For example, delete(title="MyPage") or delete(pageid=53342) are valid, while delete(title="MyPage", pageid=53342), is not. Zero arguments can not be passed. How would I go about doing this?

推荐答案

没有Python语法可让您定义异或参数，否.您必须明确地引发一个例外，即是否同时指定了两个或全部未指定:

There is no Python syntax that'll let you define exclusive-or arguments, no. You'd have to explicitly raise an exception is both or none are specified:

if (title and pageid) or not (title or pageid):
    raise ValueError('Can only delete by title OR pageid')

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