How to test if a key in a dictionary exists?

Alex Martelli aleax at
Mon Mar 12 05:19:05 CET 2007

Paul McGuire <ptmcg at> wrote:

> will be.  For instance, when working with data from 0 to 100 and
> looking for frequencies by decade, you can initialize the histogram-
> dict with:
> for i in range(10):
>     histodict[i] = 0

A better way, of course (also saving the histodict = {} which you didn't
mention but surely intended) would be:

    histodict = dict.fromkeys(range(10), 0)

In Python, in general, the more conceptually compact, direct, simple and
higher-abstraction approach tends to be faster as well, BTW.


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