[EMAIL PROTECTED] wrote: > David Murmann wrote:
>> > # New attempts: >> > from itertools import imap >> > def flatten4(x, y): >> > '''D Murman''' >> > l = [] >> > list(imap(l.extend, izip(x, y))) >> > return l >> well, i would really like to take credit for these, but they're >> not mine ;) (credit goes to Michael Spencer). i especially like >> flatten4, even if its not as fast as the phenomenally faster >> flatten7. >> > Me too. And expand a bit on flatten4, I got this interesting result. > > [EMAIL PROTECTED]:~/bonobo/psp$ python ~/lib/python2.4/timeit.py -s > "import itertools; a=zip(xrange(1000),xrange(1000))" "l=len(a); > li=[None]*l*2;li[::2]=range(1000); li[1::2]=range(1000)" > 1000 loops, best of 3: 318 usec per loop > > [EMAIL PROTECTED]:~/bonobo/psp$ python ~/lib/python2.4/timeit.py -s > "import itertools,psyco; a=zip(xrange(1000),xrange(1000));li=[]" > "filter(li.extend,a)" > 1000 loops, best of 3: 474 usec per loop For a fair comparison you'd have to time the zip operation. > Still 50% slower but it has the advantage that it works on all kinds of > sequence as they can be efficiently izip() together. 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. Peter -- http://mail.python.org/mailman/listinfo/python-list
