Python – overwrite constant from imported file and use in imported functions

Question

I have a module where some constants are defined and also used in several functions. How can I over-ride their values from my main file ?

Say this is the module, test_import.py

MY_CONST = 1

def my_func(var = MY_CONST):
    print(var)

And this is my main.py file:

import test_import

MY_CONST = 2
test_import.MY_CONST = 3

test_import.my_func()

This code still prints "1". I want it to print some other value (obviously, without passing a value when calling my_func())

Asked By: horace_vr

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Source

Answer 1

The default value is stored with the function itself when the function is defined; it is not looked up in the global scope when the function is called without an argument.

>>> test_import.my_func.__defaults__[0]
1

You can, if you really want to, assign a new default value to be used.

>>> test_import.my_func.__defaults__[0] = 9
>>> test_import.my_func()
9

Answered By: chepner

Python – overwrite constant from imported file and use in imported functions

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