[Python-Dev] Proposal: defaultdict

Guido van Rossum guido at python.org
Sat Feb 18 00:00:22 CET 2006

On 2/17/06, Adam Olsen <rhamph at gmail.com> wrote:
> > Such are the joys of writing polymorphic code. I don't really see how
> > you can avoid this kind of confusion -- I could have given you some
> > other mapping object that does weird stuff.
> You could pass a float in as well.  But if the function is documented
> as taking a dict, and the programmer expects a dict.. that now has to
> be changed to "dict without a default".  Or they have to code
> defensively since d[key] may or may not raise KeyError, so they must
> avoid depending on it either way.

I'd like to see a real-life example of code that would break this way.
I believe that *most* code that takes a dict will work just fine if
that dict has a default factory.

--Guido van Rossum (home page: http://www.python.org/~guido/)

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