From: Raymond Hettinger <python@rcn.com>
Date: Fri, 2 Apr 2010 06:21:59 +0000 (+0000)
Subject: Cleanup itertools recipes
X-Git-Tag: v2.6.6rc1~515
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=b640bcc32b21c24ced7269cc701a1ccb5569814d;p=python

Cleanup itertools recipes
---

diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
index 993e86ef01..dafeeb1537 100644
--- a/Doc/library/itertools.rst
+++ b/Doc/library/itertools.rst
@@ -663,7 +663,7 @@ which incur interpreter overhead.
 
    def ncycles(iterable, n):
        "Returns the sequence elements n times"
-       return chain.from_iterable(repeat(iterable, n))
+       return chain.from_iterable(repeat(tuple(iterable), n))
 
    def dotproduct(vec1, vec2):
        return sum(imap(operator.mul, vec1, vec2))
@@ -782,23 +782,23 @@ which incur interpreter overhead.
    def random_product(*args, **kwds):
        "Random selection from itertools.product(*args, **kwds)"
        pools = map(tuple, args) * kwds.get('repeat', 1)
-       return map(random.choice, pools)
+       return tuple(random.choice(pool) for pool in pools)
 
    def random_permuation(iterable, r=None):
        "Random selection from itertools.permutations(iterable, r)"
-       pool = list(iterable)
+       pool = tuple(iterable)
        r = len(pool) if r is None else r
-       return random.sample(pool, r)
+       return tuple(random.sample(pool, r))
 
    def random_combination(iterable, r):
        "Random selection from itertools.combinations(iterable, r)"
-       pool = list(iterable)
-       return sorted(random.sample(pool, r), key=pool.index)
+       pool = tuple(iterable)
+       return tuple(sorted(random.sample(pool, r), key=pool.index))
 
    def random_combination_with_replacement(iterable, r):
        "Random selection from itertools.combinations_with_replacement(iterable, r)"
-       pool = list(iterable)
-       return sorted(imap(random.choice, [pool]*r), key=pool.index)
+       pool = tuple(iterable)
+       return tuple(sorted(imap(random.choice, [pool]*r), key=pool.index))
 
 Note, many of the above recipes can be optimized by replacing global lookups
 with local variables defined as default values.  For example, the