Reverse dictionnary

[François Pinard]

[Julien Barbot]

> Does "reverse dictionnary" exists in python ?  I would like to get a
> value with the key, and to get the key with the value.

As others told you already, this is not always possible.  Values should
be immutable (or more precisely: hashable) and all unique.

But given the proper pre-conditions, list comprehension might be the most
legible way to go.  Still, I wonder if one would not gain some speed by
avoiding Python loops, like this maybe:

    def reverse(dictionary):
        pair = zip(*dictionary.items())
        return dict(zip(pair[1], pair[0]))

-- 
François Pinard   http://www.iro.umontreal.ca/~pinard