I ran into a case where I modified the __name__ attribute of a function 
and then didn't specify the right number of arguments, and I got a 
TypeError that used the original function name, as demonstrated here:

>>> def foo(): pass
... 
>>> foo.__name__ = 'bar'
>>> foo(1)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: foo() takes no arguments (1 given)

I would have expected it to say "TypeError: bar() ...". I'm guessing 
that the interpreter isn't using the __name__ attribute in this case.