Author terry.reedy
Recipients djc, mark.dickinson, rhettinger, terry.reedy
Date 2012-05-18.19:11:25
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Message-id <1337368286.34.0.953411246512.issue14831@psf.upfronthosting.co.za>
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permutations(i,r) has an obvious default length, len(i).
For combinations(i,r), r = len(i), the return is i itself. Uninteresting.

You are asking for something else, that combinations(i) be  powerset(i), which is a different function. Powerset can be built from chain and combinations. Raymond has rejected adding powerset, which is given in the doc in 9.1.2. Itertools Recipes. In the python-ideas 'Haskell envy' thread (about combinations/powerset), that started April 22, 2012, he said:

"The whole purpose of the itertools recipes are to teach how
the itertools can be readily combined to build new tools."

from itertools import chain, combinations

def powerset(iterable):
    pool = tuple(iterable)
    n = len(pool)
    return chain.from_iterable(combinations(pool, i) for i in range(n+1))

print(list(powerset(range(3))))

#
[(), (0,), (1,), (2,), (0, 1), (0, 2), (1, 2), (0, 1, 2)]
History
Date User Action Args
2012-05-18 19:11:26terry.reedysetrecipients: + terry.reedy, rhettinger, mark.dickinson, djc
2012-05-18 19:11:26terry.reedysetmessageid: <1337368286.34.0.953411246512.issue14831@psf.upfronthosting.co.za>
2012-05-18 19:11:25terry.reedylinkissue14831 messages
2012-05-18 19:11:25terry.reedycreate