I enjoy your explanation. I have recently written something very similar to one of my students.
We teach dictionaries about three weeks before exception handling, though, so I rarely see this code. On Tue, Dec 13, 2011 at 4:30 PM, Kirby Urner <kur...@oreillyschool.com>wrote: > Below is typical feedback to a student. > > What do others think regarding my discussion of using try /except > in routine dict manipulation? > > Kirby > > > === > > Yes perfect. Good work. > > try: > res_dict[ext] += 1 > except KeyError: > res_dict[ext] = 1 > > This code is not atypical and you'll find some polarization among > Pythonistas about whether this is good style. Another construct: > > res_dict[ext] = res_dict.get(ext, 0) + 1 > > is the one I favor. I think of a "key not found" event > in a dict as "routine, to be expected" whereas I think of > try: / except: as for "crying wolf" (not for everyday > contingencies). The opposite bias is: why make that > distinction, try: / except: is a perfectly reasonable > construct for trapping a new key to a dict. > > In any case, good Python. > > -Kirby > _______________________________________________ > Edu-sig mailing list > Edu-sig@python.org > http://mail.python.org/mailman/listinfo/edu-sig > -- Sarina Canelake MIT EECS
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