Okay, the python-dev ruling is in, and raising an exception in the __ixxx__ methods is allowed, and even a good idea in the cases of mutable containers.

However, doing the check on 'other' and raising a TypeError with an appropriate message would still be better for a couple reasons:

  - all the non-inplace operations raise TypeError when 'other' is not a correct type
  - __iand__ is currently buggy because it does not do the check

If backwards compatibility is a concern in this case, a custom "TypeError" that was a subclass of both TypeError and AttributeError could address that.