a better way to invert a list?

Raymond Hettinger python at rcn.com
Tue Apr 5 20:07:45 EDT 2011

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[Ian Kelly]
> Which is O(n).  If that is too verbose, you could also use a dictionary:
>> def invert(p):
>     return dict(map(reversed, enumerate(p)))

def inv(p):
 return dict(zip(p, itertools.count()))
Raymond

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