Faking an object in python

Question

I have a python file that contains that is part of a bigger program, that is file is used to generate some of the same data used, However while I would use this program to get the data it's so big, old and undocumented that no one know how it works.

I need to processes the data generated by these files, is there a way to mimic the modules this calls dynamically i.e. I provide an actual method that I am interested in and then I provide a fake response for any method call that hasn't been overridden.

I had an attempt at doing this with overriding the __getattrib__ method but failed horribly (I don't have the source available anymore as it got erased by mistake)

Lennart Regebro · Accepted Answer · 2013-05-30 10:51:40Z

2

Isn't it easier to just add the methods that are called?

But yes, you can fake it with for example the Mock library.

answered May 30, 2013 at 10:51

Lennart Regebro

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3 Comments

Bicker x 2 Over a year ago

no sadly it isn't as the methods called while the same a slightly different from file to file I'll have a look into the Mock Library thanks

Lennart Regebro Over a year ago

@Bickerx2 I'm not sure it would make a difference that they are slightly different. The Mock library can fake a response, but most likely you'd have to tell it what to fake so that the caller doesn't fail anyway.

Bicker x 2 Over a year ago

I think the mock library might indeed be the solution here. Otherwise I am going to have to make some serious changes to the files and then regex them (a prospect I am not looking forward to doing).

User · Accepted Answer · 2013-05-30 11:56:53Z

0

You can not fake functions like __add__ with __getattribute__.

Here you can find all methods that need to be implemented the class side e.g. __add__

I implemeted a Proxy that fakes them. It can even emulate Integers.

Once you have overwritten __getattribute__ this may come in handy.

class X(object):
    def __getattribute__(self, name): ...

    def use_this_getattribute(self):
        ... # uses getattribute from above

    @objectGetattributeFunction
    def use_original_getattribute(self):
        ...

answered May 30, 2013 at 11:56

User

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1 Comment

Bicker x 2 Over a year ago

Interesting method but considering how complex the actual code I would be hiding works (i.e. lots of unknown side-effects) I think I will be using Mock for now but, if it doesn't work I might have another look at overriding _getattribute_

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