Does anyone have a real world example outside of python's file object implementation of an __enter__ and __exit__ use case? Preferably your own, since what I'm trying to achieve is a better way to conceptualize the cases where it would be used.
I've already read this.
There are many uses. Just in the standard library we have:
sqlite3; using the connection as a context manager translates to committing or aborting the transaction.
unittest; using assertRaises as a context manager lets you assert an exception is raised, then test aspects of the exception.
decimal; localcontext manages decimal number precision, rounding, and other aspects.
threading objects such as locks, semaphores and conditions are context managers too; letting you obtain a lock for a set of statements, etc.
the warnings module gives you a context manager to temporarily catch warnings.
many libraries offer closing behaviour, just like the default file object. These include the tarfile and the zipfile modules.
Python's own test.test_support module uses several context managers, to check for specific warnings, capture stdout, ignore specific exceptions and temporarily set environment variables.
Any time you want to detect when a block of code starts and / or ends, you want to use a context manager. Where before you'd use try: with a finally: suite to guarantee a cleanup, use a context manager instead.