Context Managers: You Can Write Your Own!

Many Python newcomers won’t have seen a context manager other than with open('myfile.txt', 'r') as f, and might not even know that what they’ve been using all this time is a context manager. Context managers can be an extremely powerful tool and can save beginning programmers a lot of grief.

During this talk we’ll briefly discuss existing context managers, starting with the basics, like opening files. We’ll then move on to more obscure examples such as those in the threading module or contextlib.suppress. After this we’ll launch into writing our own context managers!

First we’ll do it the hard way, with __init__, __enter__, and __exit__ methods on a class. Then we’ll see how easily it can be done with contextlib.contextmanager and yield. Once you see how easy it is you’ll be kicking yourself for not using them more!

After this talk you should be inspired to use context managers to manage your own resources safely and make your code much prettier.