On Thu, Jul 19, 2018 at 08:57:50PM -0400, Michael Selik wrote:
Try/except also looks decent.
try: x = foo['bar'][0] except TypeError: x = 'default'
Consider the case that foo['bar'] is supposed to return either a collection (something that can be indexed) or None. But due to a bug, it returns a float 1.234. Now the try...except will *wrongly* catch the exception from 1.234[0] and return the default. The problem here is that the try...except block is NOT equivalent to the None-aware pattern: obj = foo['bar'] # avoid time-of-check-to-time-of-use bugs if obj is None: x = 'default' else: x = obj[0] except in the special case that we can guarantee that foo['bar'] can only ever return a collection or None and will never, ever be buggy. -- Steve