How to recognize default method value setting in Python? [duplicate]

Question

Consider the following class method definition in Python using default parameter values:

class X
..

    def batch(self, param="foobar", limit=2):
    ...

Then, a user could call it without arguments, just like

x.batch()

Result: the parameter values get substituted with default values.

Imagine in such case you would like to tell the user something like:

WARNING the batch size has been set to a default value 2.

Question: is there a way to backtrack either somehow intercept to recognize it (beyond simply moving this initialization and validation logic to a constructor method)?

Simon Crane · Accepted Answer · 2019-09-27 11:38:40Z

2

You can't detect when the default value is being used, but perhaps something like this?

import warnings


class X
..

    def batch(self, param="foobar", limit=None):
        if limit == None:
            limit = 2
            warnings.warn(...)

    ...

answered Sep 27, 2019 at 11:38

Simon Crane

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