[Python-checkins] cpython (merge 3.6 -> default): merge
raymond.hettinger
python-checkins at python.org
Thu Nov 17 04:50:22 EST 2016
https://hg.python.org/cpython/rev/53f5e16695d0
changeset: 105179:53f5e16695d0
parent: 105177:8fab4ba536fc
parent: 105178:3e6f23fd0c34
user: Raymond Hettinger <python at rcn.com>
date: Thu Nov 17 01:50:16 2016 -0800
summary:
merge
files:
Doc/library/random.rst | 22 ++++++++++++++--------
1 files changed, 14 insertions(+), 8 deletions(-)
diff --git a/Doc/library/random.rst b/Doc/library/random.rst
--- a/Doc/library/random.rst
+++ b/Doc/library/random.rst
@@ -152,13 +152,19 @@
.. function:: shuffle(x[, random])
- Shuffle the sequence *x* in place. The optional argument *random* is a
- 0-argument function returning a random float in [0.0, 1.0); by default, this is
- the function :func:`.random`.
+ Shuffle the sequence *x* in place.
- Note that for even rather small ``len(x)``, the total number of permutations of
- *x* is larger than the period of most random number generators; this implies
- that most permutations of a long sequence can never be generated.
+ The optional argument *random* is a 0-argument function returning a random
+ float in [0.0, 1.0); by default, this is the function :func:`.random`.
+
+ To shuffle an immutable sequence and return a new shuffled list, use
+ ``sample(x, k=len(x))`` instead.
+
+ Note that even for small ``len(x)``, the total number of permutations of *x*
+ can quickly grow larger than the period of most random number generators.
+ This implies that most permutations of a long sequence can never be
+ generated. For example, a sequence of length 2080 is the largest that
+ can fit within the period of the Mersenne Twister random number generator.
.. function:: sample(population, k)
@@ -175,9 +181,9 @@
Members of the population need not be :term:`hashable` or unique. If the population
contains repeats, then each occurrence is a possible selection in the sample.
- To choose a sample from a range of integers, use an :func:`range` object as an
+ To choose a sample from a range of integers, use a :func:`range` object as an
argument. This is especially fast and space efficient for sampling from a large
- population: ``sample(range(10000000), 60)``.
+ population: ``sample(range(10000000), k=60)``.
If the sample size is larger than the population size, a :exc:`ValueError`
is raised.
--
Repository URL: https://hg.python.org/cpython
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