Using the "with" statement wrongly results in a confusing error message.

Code (originally written by Alex Gaynor):

class Timer(object):
    def __enter__(self):
        self.start = time.time()
    def __exit__(self, exc_type, exc_val, tb):
        print "Section time: ", time.time() - self.start

#Note the error here, I call the class, not an instance
with Timer:
    pass


------------------------


Compare the Python 2.6 error:

ismael@chaos:~/Escritorio$ python bad.py 
Traceback (most recent call last):
  File "bad.py", line 8, in <module>
    with Timer:
TypeError: unbound method __enter__() must be called with Timer instance as first argument (got nothing instead)

Against Python 2.7:

ismael@chaos:~/Escritorio$ python2.7 bad.py 
Traceback (most recent call last):
  File "bad.py", line 8, in <module>
    with Timer:
AttributeError: __exit__

The message is not inaccurate, but indeed misleading. In wonder what to do considering the traditional message of AttributeError is simply the missing attribute.

Could AttributeError be improved to say something like this:

AttributeError: type 'type' has no attribute '__enter__'

As 2.7 has reached end-of-life, I'm closing the issue.