Issue 19364: Implementing __getattr__ breaks copy and deepcopy

When __getattr__ is implemented without also implementing __copy__ and __deepcopy__ trying to (deep)copy the class fails.

>>> import copy
>>> class foo():
...   def __getattr__(self, attr):
...     return None
...
>>> f = foo()
>>> copy(f)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'module' object is not callable

The copy module checks if a class has implemented __copy__ using hasattr:

if hasattr(x, '__copy__'):
  ...

An easy fix would be to use:

if getattr(x, '__copy__', None):
  ...

In Python 3 this change has already been made.

Your example worked correctly, since the copy module is indeed not copiable. :)  Did you mean "from copy import copy"?

Yes. You're correct. Sorry for the confusion. Below is an updated snippet of code.

>>> from copy import copy
>>> class foo():
...   def __getattr__(self, attr):
...     return None
... 
>>> f = foo()
>>> copy(f)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/copy.py", line 76, in copy
    return copier(x)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/copy.py", line 125, in _copy_inst
    return x.__copy__()
TypeError: 'NoneType' object is not callable

I knew this sounded familiar.  Take a look at issue16251.

resolution: duplicate
stage: resolved