itertools.islice and slice objects

[Steven Bethard]

Is there a reason that itertools.islice doesn't support None arguments 
for start and step?  This would be handy for use with slice objects:

 >>> r = range(20)
 >>> s1 = slice(2, 10, 2)
 >>> s2 = slice(2, 10)
 >>> s3 = slice(10)
 >>> list(itertools.islice(r, s1.start, s1.stop, s1.step))
[2, 4, 6, 8]
 >>> list(itertools.islice(r, s2.start, s2.stop, s2.step))
Traceback (most recent call last):
   File "<interactive input>", line 1, in ?
TypeError: an integer is required
 >>> list(itertools.islice(r, s2.start, s2.stop, s2.step or 1))
[2, 3, 4, 5, 6, 7, 8, 9]
 >>> list(itertools.islice(r, s3.start, s3.stop, s3.step))
Traceback (most recent call last):
   File "<interactive input>", line 1, in ?
TypeError: an integer is required
 >>> list(itertools.islice(r, s3.start or 0, s3.stop, s3.step or 1))
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

Of course, I can get (start, stop, step) tuples with slice.indices, but 
only if I know the length of the iterable, which kinda defeats the 
purpose of using itertools...

 >>> list(itertools.islice(r, *s2.indices(10)))
[2, 3, 4, 5, 6, 7, 8, 9]
 >>> list(itertools.islice(r, *s3.indices(10)))
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

Steve