The latter isn't actually the typical Python style. As the article discusses, Python generally prefers "EAFP"[1] to "LBYL"[2], e.g.

  def dict_breaker(some_dict):
      try:
          return parse_some_items(some_dict['items'])
      except KeyError:
          pass
    

Or even

  def dict_breaker(some_dict):
      try:
          items = some_dict['items']
      except KeyError:
          pass
      else:
          return parse_some_items(items)

These versions may be more efficient (only have to do one hash and interaction with the hashmap, but this probably won't be visible with integers/short strings), and don't suffer from race conditions in concurrent code with the hashmap being modified between the check and the use (yes, this can occur even with GIL).

[1]: https://docs.python.org/2/glossary.html#term-eafp [2]: https://docs.python.org/2/glossary.html#term-lbyl