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| author | Sergey <bizywiz@gmail.com> | 2019-10-29 05:10:24 (GMT) |
|---|---|---|
| committer | Raymond Hettinger <rhettinger@users.noreply.github.com> | 2019-10-29 05:10:24 (GMT) |
| commit | 0078a0c2a59a358fa032ec9847c108378b66b656 (patch) | |
| tree | b5a2f7ffd048d6bb763a19a077b91b266f4b57c2 /Modules | |
| parent | 3c88199e0be352c0813f145d7c4c83af044268aa (diff) | |
| download | cpython-0078a0c2a59a358fa032ec9847c108378b66b656.zip cpython-0078a0c2a59a358fa032ec9847c108378b66b656.tar.gz cpython-0078a0c2a59a358fa032ec9847c108378b66b656.tar.bz2 | |
Permutations Python code equivalent in comment was invalid for Python 3 (GH-16927)
Diffstat (limited to 'Modules')
| -rw-r--r-- | Modules/itertoolsmodule.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/Modules/itertoolsmodule.c b/Modules/itertoolsmodule.c index e60ad5b..3d39fa2 100644 --- a/Modules/itertoolsmodule.c +++ b/Modules/itertoolsmodule.c @@ -3076,12 +3076,15 @@ static PyTypeObject cwr_type = { /* permutations object ******************************************************** def permutations(iterable, r=None): - 'permutations(range(3), 2) --> (0,1) (0,2) (1,0) (1,2) (2,0) (2,1)' + # permutations('ABCD', 2) --> AB AC AD BA BC BD CA CB CD DA DB DC + # permutations(range(3)) --> 012 021 102 120 201 210 pool = tuple(iterable) n = len(pool) r = n if r is None else r - indices = range(n) - cycles = range(n-r+1, n+1)[::-1] + if r > n: + return + indices = list(range(n)) + cycles = list(range(n, n-r, -1)) yield tuple(pool[i] for i in indices[:r]) while n: for i in reversed(range(r)): |