[issue33236] MagicMock().__iter__.return_value is different from MagicMock().__iter__()

[Michael Foord]

Michael Foord  added the comment:

This isn't a bug. This is the intended behaviour, otherwise MagicMock objects 
would error out on iteration.

--
resolution:  -> not a bug
stage:  -> resolved
status: open -> closed

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[issue33236] MagicMock().__iter__.return_value is different from MagicMock().__iter__()

[Mario Corchero]

Mario Corchero  added the comment:

iter is initialized by using side_effects, not return_value.

The statement "According to the documentation .return_value should be identical 
to the object returned when calling the mock" works only when it return_value 
has been used to define the behaviour of the mock.

Example:

```
>>> m = MagicMock(side_effect=lambda: 1)
>>> m()
1
>>> m.return_value

>>> m() is m.return_value
False
```

--
nosy: +mariocj89

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[issue33236] MagicMock().__iter__.return_value is different from MagicMock().__iter__()

[Robert]

Robert  added the comment:

According to this chapter ( 
https://docs.python.org/3/library/unittest.mock.html#unittest.mock.MagicMock ) 
the specialmethods in MagicMock are different:

.return_value is preinitialized with defaultvalues, which depends on the 
operator. In the case of .__iter__ this is "iter([])".
This is the case when running __iter__(), but not when running 
__iter__.result_value

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[issue33236] MagicMock().__iter__.return_value is different from MagicMock().__iter__()

[Karthikeyan Singaravelan]

Karthikeyan Singaravelan  added the comment:

Can you please link to the relevant documentation that is misleading? As I can 
see from the source code return value is a Mock object [1] which I believe the 
docs state as below : 

https://docs.python.org/3/library/unittest.mock.html#calling

> Mock objects are callable. The call will return the value set as the 
> return_value attribute. The default return value is a new Mock object; it is 
> created the first time the return value is accessed (either explicitly or by 
> calling the Mock) - but it is stored and the same one returned each time.

from unittest.mock import MagicMock
x = MagicMock()

print(x.__iter__())
print(x.__iter__.return_value)
print(x.return_value)


➜  cpython git:(master) ./python.exe bpo33236.py





[1] : 
https://github.com/python/cpython/blob/b10a64d117de6121ea3e79c467c4107f8f399f3d/Lib/unittest/mock.py#L463


Thanks

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nosy: +xtreak

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[issue33236] MagicMock().__iter__.return_value is different from MagicMock().__iter__()

[Ned Deily]

Change by Ned Deily :


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nosy: +michael.foord

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[issue33236] MagicMock().__iter__.return_value is different from MagicMock().__iter__()

[Robert]

New submission from Robert :

According to the documentation .return_value should be identical to the object 
returned when calling the mock ("assert m() is m.return_value")

This is the case except on objects returned by __iter__ on MagicMocks. The 
following script demonstrates the problem:

from unittest.mock import MagicMock
m = MagicMock()
assert x.__iter__() is x.__iter__.return_value# <- fails


In fact __iter__() returns the object "iter([])" (which matches the 
documentation) while __iter__.return_value return a MagicMock object (which 
does not match the documentation).

When replacing "__iter__" with any other special function MagicMock works as 
expected.

--
components: Library (Lib)
messages: 315016
nosy: mrh1997
priority: normal
severity: normal
status: open
title: MagicMock().__iter__.return_value is different from 
MagicMock().__iter__()
versions: Python 2.7, Python 3.4, Python 3.5, Python 3.6

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