[TIP] MagicMocks and inequalities

[Michael Foord]

On 28 Jan 2013, at 11:16, Dan Wandschneider <daniel.wandschneider at schrodinger.com> wrote:

> Michael-
> I just downloaded mock version 1.0.1 and it still appears that __lt__ is not implemented.  I also still see the platform dependent behavior of __lt__.  I've submitted this as bug#196.

Note that MagicMock().__lt__ (and friends) returning NotImplemented is very deliberate. This platform dependent behaviour is because when comparisons return NotImplemented on *both sides* Python defaults to comparing the types. (Python 2 that is - Python 3 does the sane thing and raises a TypeError.)

The following thing returns different values on Windows and Linux/Mac:

	mock.MagicMock < int

This is odd - and is a weird platform difference in Python itself. There's nothing that mock can do about this I'm afraid. If you *care* about the result of a comparison with a magic mock then you need to be setting it explicitly. 

Sorry about that. 

Also note that in MagicMock, __lt__ (etc) *are* implemented. They are deliberately returning NotImplemented. You can change this:

>>> from mock import MagicMock
>>> m = MagicMock()
>>> m.__lt__.return_value = True
>>> m < 0
True

All the best,

Michael Foord

> Thanks-
>  Dan W.
> 
> 
> 
> On Mon, Jan 28, 2013 at 10:48 AM, Dan Wandschneider <daniel.wandschneider at schrodinger.com> wrote:
> Michael-
> Thanks for your response.  I'm using mock.py version 1.0.  I'll try to upgrade to mock 1.0.1, and if I still see this behavior, I'll definitely submit this as a bug.
> 
> Note that your test didn't really demonstrate whether __lt__ was "implemented", since it would be called even if the return value were NotImplemented.  In my copy of mock.py (version 1.0), I see this:
> _return_values = {
>     '__lt__': NotImplemented,
>     '__gt__': NotImplemented,
>     '__le__': NotImplemented,
>     '__ge__': NotImplemented,
>    etc.
> 
> And this behavior:
> 
> >>> from mock import MagicMock
> >>> m = MagicMock()
> >>> m.__lt__
> <MagicMock name='mock.__lt__' id='47908705590288'>
> >>> m.__lt__()
> NotImplemented
> >>> m < 3
> False
> >>> m.__lt__.call_count
> 2
> 
> Thanks again for this great tool,
>  Dan W.
> 
> 
> 
> 
> 
> 
> 
> On Mon, Jan 28, 2013 at 3:28 AM, Michael Foord <fuzzyman at voidspace.org.uk> wrote:
> 
> On 18 Jan 2013, at 19:52, Dan Wandschneider <daniel.wandschneider at schrodinger.com> wrote:
> 
> > Under Python 2.7.3 and Mock 1.0.0, we've noticed some strange behavior.    On Linux, 0 < MagicMock(), and on Windows 0 > MagicMock().  Has anyone else noticed similar behavior?  Should this be considered a bug?
> 
> That would be a bug, yes. One I'm very surprised about. I don't think I even have a working Windows VM to try this on though - so I'd be very interested to see if anyone else can verify it.
> 
> >
> > Note that MagicMock does not implement the inequality comparison operators, which means that in inequality comparisons it delegates the comparison to the other object.  Thus, the expression "MagicMock() > 0" is ultimately evaluated as "0 < MagicMock()."  See Lennert Regebro's cogent post about total ordering.
> 
> MagicMock *does* implement all the equality and comparison methods. The one used in a "less than" test is __lt__ :
> 
> >>> from mock import MagicMock
> >>> m = MagicMock()
> >>> m.__lt__
> <MagicMock name='mock.__lt__' id='4300924432'>
> >>> m < 0
> False
> >>> m > 0
> True
> >>> m.__lt__.call_count
> 1
> 
> All the best,
> 
> Michael Foord
> 
> > _______________________________________________
> > testing-in-python mailing list
> > testing-in-python at lists.idyll.org
> > http://lists.idyll.org/listinfo/testing-in-python
> 
> 
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> http://www.voidspace.org.uk/
> 
> 
> May you do good and not evil
> May you find forgiveness for yourself and forgive others
> May you share freely, never taking more than you give.
> -- the sqlite blessing
> http://www.sqlite.org/different.html
> 
> 
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> 
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> 


--
http://www.voidspace.org.uk/


May you do good and not evil
May you find forgiveness for yourself and forgive others
May you share freely, never taking more than you give.
-- the sqlite blessing 
http://www.sqlite.org/different.html