On Wed, 03 Aug 2011 12:15:44 +1000, Steven D'Aprano wrote: > I'm not greatly experienced with context managers and the with statement, so > I would like to check my logic. > > Somebody (doesn't matter who, or where) stated that they frequently use this > idiom: > > spam = MyContextManager(*args) > for ham in my_iter: > with spam: > # do stuff > > > but to me that looks badly wrong. Surely the spam context manager object > will exit after the first iteration, and always raise an exception on the > second? But I don't quite understand context managers enough to be sure.
It depends upon the implementation of MyContextManager. If it's implemented using the contextlib.contextmanager decorator, then you're correct: you can only use it once. OTOH, if you implement your own class with __enter__ and __exit__ methods, you can use the same context manager object multiple times. -- http://mail.python.org/mailman/listinfo/python-list
