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Newsgroups: comp.lang.python
Date: Tue, 26 Apr 2011 12:39:32 -0700 (PDT)
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Subject: Re: De-tupleizing a list
From: Mark Niemczyk <prahamark@gmail.com>
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:4074

Some interesting performance comparisons, under Python 3.2.  Times are relative, and are for an initial list of tuples with 500,000 items.  

(1)    ans = []                                                                 #relative time: 298
         for item in lst:
             ans += list(item)
         return ans

(2)    return [item[0] for item in lst]                          #relative time:  106

(3)    from operator import itemgetter                     #relative time:   84
         return list(map(itemgetter(0), lst))

(4)    import itertools                                                   #relative time:  63
         return list(itertools.chain.from_iterable(lst))

(5)    return [x for (x,) in lst]                                      #relative time:  52


With the caveat that 'your mileage may vary'

Regards,
Mark