[EMAIL PROTECTED] wrote: >> Creating a list via list/map/filter just for the side effect is not only >> bad taste, >> >> ~ $ python -m timeit -s'a = zip([range(1000)]*2)' 'lst=[];ext=lst.extend' >> 'for i in a: ext(i)' >> 1000000 loops, best of 3: 1.23 usec per loop >> ~ $ python -m timeit -s'a = zip([range(1000)]*2)' >> 'lst=[];filter(lst.extend, a)' >> 1000000 loops, best of 3: 1.63 usec per loop >> >> it is also slower than an explicit loop. Don't do it. >> > Hi, but I found this result instead : > > [EMAIL PROTECTED]:~$ python ~/lib/python2.4/timeit.py -s "a=range(10000); > b=zip(*[a]*2); l=[None]*len(a)*2; e=l.extend" "l[::2]=b;l[1::2]=b" > 100 loops, best of 3: 6.22 msec per loop > [EMAIL PROTECTED]:~$ python ~/lib/python2.4/timeit.py -s "a=range(10000); > b=zip(*[a]*2); l=[]; e=l.extend" "filter(e,b)" > 100 loops, best of 3: 7.25 msec per loop > [EMAIL PROTECTED]:~$ python ~/lib/python2.4/timeit.py -s "a=range(10000); > b=zip(*[a]*2); l=[]; e=l.extend" "for x in b: e(x)" > 100 loops, best of 3: 10.7 msec per loop > [EMAIL PROTECTED]:~$ > > So it seems to be faster than explicit loop. By localizing the l.extend > name binding, its speed is only 20% slower than the fastest method. > May be I have done something wrong in the test ?
I hate to admit it but /my/ post had a bug: zip([range(1000)]*2) should have been zip(*[range(1000)]*2). filter() may be ugly, but faster it is. Peter -- http://mail.python.org/mailman/listinfo/python-list
