- Issue 4816: itertools.combinations() and itertools.product were raising
a ValueError for values of *r* larger than the input iterable. They now
correctly return an empty iterator.
diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
index 67646c6..aef3f6a 100644
--- a/Doc/library/itertools.rst
+++ b/Doc/library/itertools.rst
@@ -108,6 +108,8 @@
# combinations(range(4), 3) --> 012 013 023 123
pool = tuple(iterable)
n = len(pool)
+ if r > n:
+ return
indices = range(r)
yield tuple(pool[i] for i in indices)
while 1:
@@ -132,6 +134,9 @@
if sorted(indices) == list(indices):
yield tuple(pool[i] for i in indices)
+ The number of items returned is ``n! / r! / (n-r)!`` when ``0 <= r <= n``
+ or zero when ``r > n``.
+
.. versionadded:: 2.6
.. function:: count([n])
@@ -399,6 +404,8 @@
pool = tuple(iterable)
n = len(pool)
r = n if r is None else r
+ if r > n:
+ return
indices = range(n)
cycles = range(n, n-r, -1)
yield tuple(pool[i] for i in indices[:r])
@@ -428,6 +435,9 @@
if len(set(indices)) == r:
yield tuple(pool[i] for i in indices)
+ The number of items returned is ``n! / (n-r)!`` when ``0 <= r <= n``
+ or zero when ``r > n``.
+
.. versionadded:: 2.6
.. function:: product(*iterables[, repeat])
@@ -674,7 +684,8 @@
return (d for d, s in izip(data, selectors) if s)
def combinations_with_replacement(iterable, r):
- "combinations_with_replacement('ABC', 3) --> AA AB AC BB BC CC"
+ "combinations_with_replacement('ABC', 2) --> AA AB AC BB BC CC"
+ # number items returned: (n+r-1)! / r! / (n-1)!
pool = tuple(iterable)
n = len(pool)
indices = [0] * r