candide, 22.04.2010 09:10:
Suppose a and b are lists.
What is more efficient in order to extend the list a by appending all
the items in the list b ?
I imagine a.extend(b)to be more efficient for only appendinding the
items from b while a+=b creates a copy of a before appending, right ?
Wrong.
Try it out yourself:
$ python2.6 -m timeit -s "l=range(1000)" "a=l[:]; a+=l"
100000 loops, best of 3: 9.16 usec per loop
$ python2.6 -m timeit -s "l=range(1000)" "a=l[:]; a.extend(l)"
100000 loops, best of 3: 9.24 usec per loop
$ python2.6 -m timeit -s "l=range(10000)" "a=l[:]; a.extend(l)"
10000 loops, best of 3: 96 usec per loop
$ python2.6 -m timeit -s "l=range(10000)" "a=l[:]; a+=l"
10000 loops, best of 3: 96.7 usec per loop
$ python2.6 -m timeit -s "l=range(10000)" "a=l[:]; a+=l; a+=l"
10000 loops, best of 3: 151 usec per loop
$ python2.6 -m timeit -s "l=range(10000)" \
"a=l[:]; a.extend(l); a.extend(l)"
1000 loops, best of 3: 164 usec per loop
Stefan
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