有什么方法可以知道参数的值是默认值还是用户指定的值? [英] Is there any way to know if the value of an argument is the default vs. user-specified?

问题描述

我正在寻找类似于 Lisp 的 arg-supplied-p 变量的东西，以帮助区分默认值和用户指定的相同值.

I'm looking for something that works like Lisp's arg-supplied-p variables, to help differentiate a default value from the same value specified by a user.

示例:

def foo(a=10):
    pass

我想在 foo 中知道它是否是这样调用的:

I'd like to know in foo if it was called like this:

foo()

或者像这样:

foo(10)

甚至像这样:

foo(a=10)

最后两个对我来说是同义词；我不需要知道那个细节.我稍微浏览了检查模块，但 getargspec 为所有 3 次调用返回完全相同的结果.

The last 2 are synonymous enough to me; I don't need to know that detail. I've looked through the inspect module a bit, but getargspec returns exactly the same results for all 3 calls.

推荐答案

除了检查源代码，没有办法区分这三个函数调用——它们意味着相同的含义.如果您需要区分它们，请使用不同的默认值，例如无.

Except for inspecting the source code, there is no way to tell the three function calls apart – they are meant to have exactly the same meaning. If you need to differentiate between them, use a different default value, e.g. None.

def foo(a=None):
    if a is None:
        a = 10
        # no value for a provided

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