有没有办法知道如果一个参数的值是默认与用户指定的？ [英] Is there any way to know if the value of an argument is the default vs. user-specified?

问题描述

我在找的东西，就像Lisp语言的ARG提供-P的变量，以帮助区分由用户指定的值相同的默认值。

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.

例如：

def foo(a=10):
    pass

我想在富知道，如果它被称为是这样的：

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

foo()

或者是这样的：

foo(10)

甚至是这样的：

foo(a=10)

最后2有足够的代名词给我;我并不需要知道的细节。我已经通过了检查模块看上去有点，但getargspec所有3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$ C ​​$ C，有没有办法告诉三个函数调用外 - 他们的意味着的到具有完全相同的含义。如果你需要区分它们，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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