In article <[EMAIL PROTECTED]>,
Skip Montanaro <[EMAIL PROTECTED]> wrote:
>
>Assuming your dictionary defines a one-to-one mapping, just invert it:
>
> >>> forward = {10 : 50, 2 : 12, 4 : 43}
> >>> reverse = dict([(v,k) for (k,v) in forward.iteritems()])
> >>> print forward
> {10: 50, 4: 43, 2: 12}
> >>> print reverse
> {50: 10, 43: 4, 12: 2}
>
>That doubles your storage, so you'll have to trade that off against the
>speed gain of not having to loop over the entire dictionary.
To be precise, it doubles the storage of the *dictionary*, but it does
*NOT* double the storage of the keys and items. Depending on how big
those are, the cost of building a second dict might be mostly lost in the
noise.
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