Python mock patch a function decorator's parameter value

Question

Lets say I have a settings.py

value = 10

and I have a function like this with a decorator inside module a

import settings

@some_decorator(repeat=settings.value):
def do_work():
   print settings.value
   // prints 1
   ...

In unittest I am trying to patch the settings.value to 1 like this:

with patch('settings.value', new=1):
    do_work()

But the do_work function still gets repeated 10 times, I don't think the parameter of the decorator was patched because it gets executed before the unittest starts. How do I change this?

@alecxe not exactly, it's an App setting in v1.7, I just simplified it for SO. — James Lin
– James Lin, Commented Nov 18, 2014 at 2:35

blue · Accepted Answer · 2023-08-09 15:29:56Z

1

In short you cannot patch a value passed to a decorator parameter.

Anyway, your patch does not work because when do_work() is decorated settings.value was 10 and you cannot change it after that: it is not a variable that is resolved at run time but just a value (not mutable).

Of course, when do_work() is executed settings.value is 1 and then it prints 1 but the value used in decorated do_work() is still 10 and cannot change.

How you can work around it? If you cannot change the decorator I cannot see any way to do it, otherwise if repeat in the decorator is a callable, it will be resolved every time you call the decorated function.

edited Aug 9, 2023 at 15:29

blue

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answered Nov 18, 2014 at 9:46

Michele d'Amico

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Comments

John Mee · Accepted Answer · 2014-11-18 02:40:34Z

0

Try overriding the settings?

https://docs.djangoproject.com/en/1.7/topics/testing/tools/#overriding-settings

@override_settings(LOGIN_URL='/other/login/')
def test_login(self):

answered Nov 18, 2014 at 2:40

John Mee

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1 Comment

James Lin Over a year ago

I am curious if it would be too late to modify the settings since the module gets parsed before changing the settings?

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