cpython-lru_cache-weakref: Doc/library/random.rst annotate

annotate Doc/library/random.rst @ 54294:dba767bc3155 legacy-trunk

remove mention of old ctypes version

author	Benjamin Peterson <benjamin@python.org>
date	Sat, 23 May 2009 20:59:09 +0000
parents	2a27f9ada8e3
children	7cf89ed90f9d

rev	line source
42603 c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	1
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	2 :mod:`random` --- Generate pseudo-random numbers
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	3 ================================================
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	4
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	5 .. module:: random
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	6 :synopsis: Generate pseudo-random numbers with various common distributions.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	7
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	8
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	9 This module implements pseudo-random number generators for various
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	10 distributions.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	11
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	12 For integers, uniform selection from a range. For sequences, uniform selection
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	13 of a random element, a function to generate a random permutation of a list
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	14 in-place, and a function for random sampling without replacement.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	15
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	16 On the real line, there are functions to compute uniform, normal (Gaussian),
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	17 lognormal, negative exponential, gamma, and beta distributions. For generating
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	18 distributions of angles, the von Mises distribution is available.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	19
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	20 Almost all module functions depend on the basic function :func:`random`, which
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	21 generates a random float uniformly in the semi-open range [0.0, 1.0). Python
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	22 uses the Mersenne Twister as the core generator. It produces 53-bit precision
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	23 floats and has a period of 2\\19937-1. The underlying implementation in C is
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	24 both fast and threadsafe. The Mersenne Twister is one of the most extensively
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	25 tested random number generators in existence. However, being completely
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	26 deterministic, it is not suitable for all purposes, and is completely unsuitable
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	27 for cryptographic purposes.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	28
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	29 The functions supplied by this module are actually bound methods of a hidden
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	30 instance of the :class:`random.Random` class. You can instantiate your own
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	31 instances of :class:`Random` to get generators that don't share state. This is
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	32 especially useful for multi-threaded programs, creating a different instance of
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	33 :class:`Random` for each thread, and using the :meth:`jumpahead` method to make
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	34 it likely that the generated sequences seen by each thread don't overlap.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	35
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	36 Class :class:`Random` can also be subclassed if you want to use a different
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	37 basic generator of your own devising: in that case, override the :meth:`random`,
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	38 :meth:`seed`, :meth:`getstate`, :meth:`setstate` and :meth:`jumpahead` methods.
48100 40e949a68344 getrandombits is actually getrandbits Benjamin Peterson <benjamin@python.org> parents: 46046 diff changeset	39 Optionally, a new generator can supply a :meth:`getrandbits` method --- this
42603 c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	40 allows :meth:`randrange` to produce selections over an arbitrarily large range.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	41
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	42 .. versionadded:: 2.4
48100 40e949a68344 getrandombits is actually getrandbits Benjamin Peterson <benjamin@python.org> parents: 46046 diff changeset	43 the :meth:`getrandbits` method.
42603 c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	44
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	45 As an example of subclassing, the :mod:`random` module provides the
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	46 :class:`WichmannHill` class that implements an alternative generator in pure
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	47 Python. The class provides a backward compatible way to reproduce results from
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	48 earlier versions of Python, which used the Wichmann-Hill algorithm as the core
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	49 generator. Note that this Wichmann-Hill generator can no longer be recommended:
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	50 its period is too short by contemporary standards, and the sequence generated is
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	51 known to fail some stringent randomness tests. See the references below for a
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	52 recent variant that repairs these flaws.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	53
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	54 .. versionchanged:: 2.3
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	55 Substituted MersenneTwister for Wichmann-Hill.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	56
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	57 Bookkeeping functions:
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	58
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	59
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	60 .. function:: seed([x])
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	61
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	62 Initialize the basic random number generator. Optional argument x can be any
43753 4b3623568e6c Make "hashable" a glossary entry and clarify docs on __cmp__, __eq__ and __hash__. Georg Brandl <georg@python.org> parents: 42603 diff changeset	63 :term:`hashable` object. If x is omitted or ``None``, current system time is used;
42603 c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	64 current system time is also used to initialize the generator when the module is
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	65 first imported. If randomness sources are provided by the operating system,
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	66 they are used instead of the system time (see the :func:`os.urandom` function
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	67 for details on availability).
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	68
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	69 .. versionchanged:: 2.4
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	70 formerly, operating system resources were not used.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	71
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	72 If x is not ``None`` or an int or long, ``hash(x)`` is used instead. If x is
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	73 an int or long, x is used directly.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	74
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	75
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	76 .. function:: getstate()
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	77
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	78 Return an object capturing the current internal state of the generator. This
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	79 object can be passed to :func:`setstate` to restore the state.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	80
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	81 .. versionadded:: 2.1
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	82
44122 97210d863d12 Issue #1727780: Support loading pickles of random.Random objects created Martin v. Löwis <martin@v.loewis.de> parents: 43849 diff changeset	83 .. versionchanged:: 2.6
97210d863d12 Issue #1727780: Support loading pickles of random.Random objects created Martin v. Löwis <martin@v.loewis.de> parents: 43849 diff changeset	84 State values produced in Python 2.6 cannot be loaded into earlier versions.
97210d863d12 Issue #1727780: Support loading pickles of random.Random objects created Martin v. Löwis <martin@v.loewis.de> parents: 43849 diff changeset	85
42603 c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	86
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	87 .. function:: setstate(state)
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	88
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	89 state should have been obtained from a previous call to :func:`getstate`, and
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	90 :func:`setstate` restores the internal state of the generator to what it was at
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	91 the time :func:`setstate` was called.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	92
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	93 .. versionadded:: 2.1
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	94
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	95
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	96 .. function:: jumpahead(n)
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	97
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	98 Change the internal state to one different from and likely far away from the
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	99 current state. n is a non-negative integer which is used to scramble the
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	100 current state vector. This is most useful in multi-threaded programs, in
45429 853af5bbb497 A lot more typo fixes by Ori Avtalion. Georg Brandl <georg@python.org> parents: 44122 diff changeset	101 conjunction with multiple instances of the :class:`Random` class:
42603 c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	102 :meth:`setstate` or :meth:`seed` can be used to force all instances into the
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	103 same internal state, and then :meth:`jumpahead` can be used to force the
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	104 instances' states far apart.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	105
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	106 .. versionadded:: 2.1
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	107
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	108 .. versionchanged:: 2.3
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	109 Instead of jumping to a specific state, n steps ahead, ``jumpahead(n)``
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	110 jumps to another state likely to be separated by many steps.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	111
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	112
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	113 .. function:: getrandbits(k)
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	114
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	115 Returns a python :class:`long` int with k random bits. This method is supplied
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	116 with the MersenneTwister generator and some other generators may also provide it
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	117 as an optional part of the API. When available, :meth:`getrandbits` enables
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	118 :meth:`randrange` to handle arbitrarily large ranges.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	119
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	120 .. versionadded:: 2.4
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	121
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	122 Functions for integers:
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	123
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	124
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	125 .. function:: randrange([start,] stop[, step])
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	126
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	127 Return a randomly selected element from ``range(start, stop, step)``. This is
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	128 equivalent to ``choice(range(start, stop, step))``, but doesn't actually build a
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	129 range object.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	130
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	131 .. versionadded:: 1.5.2
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	132
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	133
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	134 .. function:: randint(a, b)
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	135
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	136 Return a random integer N such that ``a <= N <= b``.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	137
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	138 Functions for sequences:
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	139
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	140
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	141 .. function:: choice(seq)
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	142
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	143 Return a random element from the non-empty sequence seq. If seq is empty,
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	144 raises :exc:`IndexError`.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	145
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	146
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	147 .. function:: shuffle(x[, random])
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	148
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	149 Shuffle the sequence x in place. The optional argument random is a
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	150 0-argument function returning a random float in [0.0, 1.0); by default, this is
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	151 the function :func:`random`.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	152
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	153 Note that for even rather small ``len(x)``, the total number of permutations of
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	154 x is larger than the period of most random number generators; this implies
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	155 that most permutations of a long sequence can never be generated.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	156
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	157
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	158 .. function:: sample(population, k)
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	159
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	160 Return a k length list of unique elements chosen from the population sequence.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	161 Used for random sampling without replacement.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	162
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	163 .. versionadded:: 2.3
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	164
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	165 Returns a new list containing elements from the population while leaving the
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	166 original population unchanged. The resulting list is in selection order so that
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	167 all sub-slices will also be valid random samples. This allows raffle winners
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	168 (the sample) to be partitioned into grand prize and second place winners (the
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	169 subslices).
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	170
43753 4b3623568e6c Make "hashable" a glossary entry and clarify docs on __cmp__, __eq__ and __hash__. Georg Brandl <georg@python.org> parents: 42603 diff changeset	171 Members of the population need not be :term:`hashable` or unique. If the population
42603 c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	172 contains repeats, then each occurrence is a possible selection in the sample.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	173
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	174 To choose a sample from a range of integers, use an :func:`xrange` object as an
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	175 argument. This is especially fast and space efficient for sampling from a large
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	176 population: ``sample(xrange(10000000), 60)``.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	177
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	178 The following functions generate specific real-valued distributions. Function
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	179 parameters are named after the corresponding variables in the distribution's
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	180 equation, as used in common mathematical practice; most of these equations can
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	181 be found in any statistics text.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	182
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	183
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	184 .. function:: random()
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	185
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	186 Return the next random floating point number in the range [0.0, 1.0).
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	187
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	188
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	189 .. function:: uniform(a, b)
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	190
51809 a366688a8f0d Merged revisions 68582,68718,68720-68721,68724-68727,68859,68973,69288-69289,69293,69295,69297-69301,69409,69414,69570,69573,69576,69728-69730,69769,69776,69803-69805,69840,69896 via svnmerge from Georg Brandl <georg@python.org> parents: 50786 diff changeset	191 Return a random floating point number N such that ``a <= N <= b`` for
a366688a8f0d Merged revisions 68582,68718,68720-68721,68724-68727,68859,68973,69288-69289,69293,69295,69297-69301,69409,69414,69570,69573,69576,69728-69730,69769,69776,69803-69805,69840,69896 via svnmerge from Georg Brandl <georg@python.org> parents: 50786 diff changeset	192 ``a <= b`` and ``b <= N <= a`` for ``b < a``.
49253 923fb458bd0c #3918: note that uniform() args can be swapped. Georg Brandl <georg@python.org> parents: 48100 diff changeset	193
42603 c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	194
46029 f1e51785947f Issue 1681432: Add triangular distribution the random module. Raymond Hettinger <python@rcn.com> parents: 45429 diff changeset	195 .. function:: triangular(low, high, mode)
f1e51785947f Issue 1681432: Add triangular distribution the random module. Raymond Hettinger <python@rcn.com> parents: 45429 diff changeset	196
51809 a366688a8f0d Merged revisions 68582,68718,68720-68721,68724-68727,68859,68973,69288-69289,69293,69295,69297-69301,69409,69414,69570,69573,69576,69728-69730,69769,69776,69803-69805,69840,69896 via svnmerge from Georg Brandl <georg@python.org> parents: 50786 diff changeset	197 Return a random floating point number N such that ``low <= N <= high`` and
46046 8c2604fe5886 Tighten documentation for Random.triangular. Raymond Hettinger <python@rcn.com> parents: 46030 diff changeset	198 with the specified mode between those bounds. The low and high bounds
8c2604fe5886 Tighten documentation for Random.triangular. Raymond Hettinger <python@rcn.com> parents: 46030 diff changeset	199 default to zero and one. The mode argument defaults to the midpoint
8c2604fe5886 Tighten documentation for Random.triangular. Raymond Hettinger <python@rcn.com> parents: 46030 diff changeset	200 between the bounds, giving a symmetric distribution.
46030 1d5a11619eca Adopt Nick's suggestion for useful default arguments. Raymond Hettinger <python@rcn.com> parents: 46029 diff changeset	201
46046 8c2604fe5886 Tighten documentation for Random.triangular. Raymond Hettinger <python@rcn.com> parents: 46030 diff changeset	202 .. versionadded:: 2.6
46030 1d5a11619eca Adopt Nick's suggestion for useful default arguments. Raymond Hettinger <python@rcn.com> parents: 46029 diff changeset	203
42603 c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	204
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	205 .. function:: betavariate(alpha, beta)
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	206
51809 a366688a8f0d Merged revisions 68582,68718,68720-68721,68724-68727,68859,68973,69288-69289,69293,69295,69297-69301,69409,69414,69570,69573,69576,69728-69730,69769,69776,69803-69805,69840,69896 via svnmerge from Georg Brandl <georg@python.org> parents: 50786 diff changeset	207 Beta distribution. Conditions on the parameters are ``alpha > 0`` and
a366688a8f0d Merged revisions 68582,68718,68720-68721,68724-68727,68859,68973,69288-69289,69293,69295,69297-69301,69409,69414,69570,69573,69576,69728-69730,69769,69776,69803-69805,69840,69896 via svnmerge from Georg Brandl <georg@python.org> parents: 50786 diff changeset	208 ``beta > 0``. Returned values range between 0 and 1.
42603 c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	209
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	210
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	211 .. function:: expovariate(lambd)
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	212
50786 2d453b221bec Merged revisions 68292,68344,68361,68378,68424,68426,68429-68430,68450,68457,68480-68481,68493,68495,68499,68501,68512,68514-68515 via svnmerge from Georg Brandl <georg@python.org> parents: 49253 diff changeset	213 Exponential distribution. lambd is 1.0 divided by the desired
2d453b221bec Merged revisions 68292,68344,68361,68378,68424,68426,68429-68430,68450,68457,68480-68481,68493,68495,68499,68501,68512,68514-68515 via svnmerge from Georg Brandl <georg@python.org> parents: 49253 diff changeset	214 mean. It should be nonzero. (The parameter would be called
2d453b221bec Merged revisions 68292,68344,68361,68378,68424,68426,68429-68430,68450,68457,68480-68481,68493,68495,68499,68501,68512,68514-68515 via svnmerge from Georg Brandl <georg@python.org> parents: 49253 diff changeset	215 "lambda", but that is a reserved word in Python.) Returned values
2d453b221bec Merged revisions 68292,68344,68361,68378,68424,68426,68429-68430,68450,68457,68480-68481,68493,68495,68499,68501,68512,68514-68515 via svnmerge from Georg Brandl <georg@python.org> parents: 49253 diff changeset	216 range from 0 to positive infinity if lambd is positive, and from
2d453b221bec Merged revisions 68292,68344,68361,68378,68424,68426,68429-68430,68450,68457,68480-68481,68493,68495,68499,68501,68512,68514-68515 via svnmerge from Georg Brandl <georg@python.org> parents: 49253 diff changeset	217 negative infinity to 0 if lambd is negative.
42603 c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	218
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	219
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	220 .. function:: gammavariate(alpha, beta)
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	221
51809 a366688a8f0d Merged revisions 68582,68718,68720-68721,68724-68727,68859,68973,69288-69289,69293,69295,69297-69301,69409,69414,69570,69573,69576,69728-69730,69769,69776,69803-69805,69840,69896 via svnmerge from Georg Brandl <georg@python.org> parents: 50786 diff changeset	222 Gamma distribution. (Not the gamma function!) Conditions on the
a366688a8f0d Merged revisions 68582,68718,68720-68721,68724-68727,68859,68973,69288-69289,69293,69295,69297-69301,69409,69414,69570,69573,69576,69728-69730,69769,69776,69803-69805,69840,69896 via svnmerge from Georg Brandl <georg@python.org> parents: 50786 diff changeset	223 parameters are ``alpha > 0`` and ``beta > 0``.
42603 c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	224
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	225
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	226 .. function:: gauss(mu, sigma)
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	227
51809 a366688a8f0d Merged revisions 68582,68718,68720-68721,68724-68727,68859,68973,69288-69289,69293,69295,69297-69301,69409,69414,69570,69573,69576,69728-69730,69769,69776,69803-69805,69840,69896 via svnmerge from Georg Brandl <georg@python.org> parents: 50786 diff changeset	228 Gaussian distribution. mu is the mean, and sigma is the standard
a366688a8f0d Merged revisions 68582,68718,68720-68721,68724-68727,68859,68973,69288-69289,69293,69295,69297-69301,69409,69414,69570,69573,69576,69728-69730,69769,69776,69803-69805,69840,69896 via svnmerge from Georg Brandl <georg@python.org> parents: 50786 diff changeset	229 deviation. This is slightly faster than the :func:`normalvariate` function
a366688a8f0d Merged revisions 68582,68718,68720-68721,68724-68727,68859,68973,69288-69289,69293,69295,69297-69301,69409,69414,69570,69573,69576,69728-69730,69769,69776,69803-69805,69840,69896 via svnmerge from Georg Brandl <georg@python.org> parents: 50786 diff changeset	230 defined below.
42603 c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	231
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	232
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	233 .. function:: lognormvariate(mu, sigma)
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	234
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	235 Log normal distribution. If you take the natural logarithm of this
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	236 distribution, you'll get a normal distribution with mean mu and standard
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	237 deviation sigma. mu can have any value, and sigma must be greater than
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	238 zero.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	239
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	240
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	241 .. function:: normalvariate(mu, sigma)
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	242
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	243 Normal distribution. mu is the mean, and sigma is the standard deviation.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	244
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	245
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	246 .. function:: vonmisesvariate(mu, kappa)
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	247
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	248 mu is the mean angle, expressed in radians between 0 and 2\\ pi, and kappa*
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	249 is the concentration parameter, which must be greater than or equal to zero. If
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	250 kappa is equal to zero, this distribution reduces to a uniform random angle
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	251 over the range 0 to 2\\ pi*.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	252
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	253
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	254 .. function:: paretovariate(alpha)
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	255
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	256 Pareto distribution. alpha is the shape parameter.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	257
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	258
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	259 .. function:: weibullvariate(alpha, beta)
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	260
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	261 Weibull distribution. alpha is the scale parameter and beta is the shape
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	262 parameter.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	263
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	264
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	265 Alternative Generators:
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	266
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	267 .. class:: WichmannHill([seed])
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	268
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	269 Class that implements the Wichmann-Hill algorithm as the core generator. Has all
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	270 of the same methods as :class:`Random` plus the :meth:`whseed` method described
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	271 below. Because this class is implemented in pure Python, it is not threadsafe
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	272 and may require locks between calls. The period of the generator is
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	273 6,953,607,871,644 which is small enough to require care that two independent
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	274 random sequences do not overlap.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	275
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	276
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	277 .. function:: whseed([x])
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	278
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	279 This is obsolete, supplied for bit-level compatibility with versions of Python
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	280 prior to 2.1. See :func:`seed` for details. :func:`whseed` does not guarantee
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	281 that distinct integer arguments yield distinct internal states, and can yield no
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	282 more than about 2\\24 distinct internal states in all.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	283
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	284
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	285 .. class:: SystemRandom([seed])
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	286
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	287 Class that uses the :func:`os.urandom` function for generating random numbers
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	288 from sources provided by the operating system. Not available on all systems.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	289 Does not rely on software state and sequences are not reproducible. Accordingly,
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	290 the :meth:`seed` and :meth:`jumpahead` methods have no effect and are ignored.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	291 The :meth:`getstate` and :meth:`setstate` methods raise
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	292 :exc:`NotImplementedError` if called.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	293
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	294 .. versionadded:: 2.4
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	295
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	296 Examples of basic usage::
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	297
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	298 >>> random.random() # Random float x, 0.0 <= x < 1.0
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	299 0.37444887175646646
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	300 >>> random.uniform(1, 10) # Random float x, 1.0 <= x < 10.0
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	301 1.1800146073117523
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	302 >>> random.randint(1, 10) # Integer from 1 to 10, endpoints included
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	303 7
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	304 >>> random.randrange(0, 101, 2) # Even integer from 0 to 100
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	305 26
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	306 >>> random.choice('abcdefghij') # Choose a random element
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	307 'c'
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	308
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	309 >>> items = [1, 2, 3, 4, 5, 6, 7]
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	310 >>> random.shuffle(items)
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	311 >>> items
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	312 [7, 3, 2, 5, 6, 4, 1]
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	313
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	314 >>> random.sample([1, 2, 3, 4, 5], 3) # Choose 3 elements
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	315 [4, 1, 5]
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	316
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	317
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	318
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	319 .. seealso::
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	320
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	321 M. Matsumoto and T. Nishimura, "Mersenne Twister: A 623-dimensionally
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	322 equidistributed uniform pseudorandom number generator", ACM Transactions on
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	323 Modeling and Computer Simulation Vol. 8, No. 1, January pp.3-30 1998.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	324
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	325 Wichmann, B. A. & Hill, I. D., "Algorithm AS 183: An efficient and portable
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	326 pseudo-random number generator", Applied Statistics 31 (1982) 188-190.
c62f6669ae22 Move the 2.6 reST doc tree in place. Georg Brandl <georg@python.org> parents: diff changeset	327
52679 f942893fa4d8 Add link to an alternative generator with a long-period. Raymond Hettinger <python@rcn.com> parents: 51809 diff changeset	328 `Complementary-Multiply-with-Carry recipe
52762 2a27f9ada8e3 Fix typo. Raymond Hettinger <python@rcn.com> parents: 52679 diff changeset	329 <http://code.activestate.com/recipes/576707/>`_ for a compatible alternative
2a27f9ada8e3 Fix typo. Raymond Hettinger <python@rcn.com> parents: 52679 diff changeset	330 random number generator with a long period and comparatively simple update
52679 f942893fa4d8 Add link to an alternative generator with a long-period. Raymond Hettinger <python@rcn.com> parents: 51809 diff changeset	331 operations.

Mercurial > cpython-lru_cache-weakref

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