python - AttributeError: module 'attr' has no attribute 's'

Question

>>> import attr
>>> @attr.s
... class SmartClass(object):
...     a=attr.ib()
...     b=attr.ib()
... 
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: module 'attr' has no attribute 's'
>>> 

I don't understand why it's not working. I have installed this module using pip and it was installed properly, but still it shows an error in the implementation part.

Answer 1

The attr library on PyPI does not have an API that looks like this. There's no attr.ib or attr.s in it, and so no reason you should expect it to work.

You're probably using documentation for the attrs library, which—somewhat confusingly—installs packages named both attrs and attr, and does in fact have an attr.s and an attr.ib, used exactly the way you're attempting.

But if you want to use the attrs library, you have to install it—and you probably want to uninstall attr too:

$ pip uninstall attr
$ pip install attrs

(If you actually want both, it's a bit confusing; the recommended way seems to be to use attr from attrs, and dry_attr from attr.)

Of course the best solution is to hop in a time machine to a few months in the future so you can use Python 3.7, with its PEP 557 data classes, a feature based largely on attrs, but simpler and built in to the stdlib.