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Follow-up to ticket 10227. The following facts seem to indicate that it would be worth caching constant instances of the slice type, such as in [:] or [:-1].
with cached slice instance:
$ ./python -m timeit -s 'l = list(range(100)); s=slice(None)' 'l[s]'
1000000 loops, best of 3: 0.464 usec per loop
$ ./python -m timeit -s 'l = list(range(10)); s=slice(None)' 'l[s]'
10000000 loops, best of 3: 0.149 usec per loop
$ ./python -m timeit -s 'l = list(range(10)); s=slice(None,1)' 'l[s]'
10000000 loops, best of 3: 0.135 usec per loop
uncached normal usage:
$ ./python -m timeit -s 'l = list(range(100))' 'l[:]'
1000000 loops, best of 3: 0.499 usec per loop
$ ./python -m timeit -s 'l = list(range(100))' 'l[:1]'
10000000 loops, best of 3: 0.171 usec per loop
Timings based on Python 3.2 rc2.
A quick grep against the py3k stdlib finds 2096 lines in 393 files that use constant slices.