Well, at least from a maintainability perspective it's more clear to do try: afile = open('myfile.txt') content = afile.read() except XXX: (han

Well, at least from a maintainability perspective it's more clear to do try: afile = open('myfile.txt') content = afile.read() except XXX: (handle exception) else: (continue here using content) If you want to capture the exceptions from a certain call. Otherwise, my_library.do_something might start raising a IOError somewhere in its bowels later on, and you have a confusing debug process. When you find that you have a lot of similar or even repeated try/catch blocks, using 'with' context managers might be a good idea. My point was that an IOError is an IOError, wether it's a MongoDBIOError or a MySQLIOError. Yes, you leak some implementation detail (namely, that I/O is used) but do do useful diagnostics you need some (abstract) implementation knowledge... network error: is your router plugged in? io error: is the disk full? keyerror: implementation bug? and so on. Hm maybe this would be a case for multi-inheritance exceptions? MongoDBIOException is both and IOException as a MongoDBException. Don't even know if it's possible, or wise :)