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__