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author | Raymond Hettinger <python@rcn.com> | 2016-11-21 20:34:12 (GMT) |
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committer | Raymond Hettinger <python@rcn.com> | 2016-11-21 20:34:12 (GMT) |
commit | c34e8604c85cf3c9e692a265b879f861dd38e198 (patch) | |
tree | f495b6d1ab3ec759f39e77bb53a967a0848669d5 /Doc | |
parent | 46d8e3181e10c91d17fdbbc225664476cdf6c732 (diff) | |
parent | e1329105b355b83c75f9bdb7471494d01a7d8705 (diff) | |
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Diffstat (limited to 'Doc')
-rw-r--r-- | Doc/library/random.rst | 57 |
1 files changed, 31 insertions, 26 deletions
diff --git a/Doc/library/random.rst b/Doc/library/random.rst index 39528df..4d0c8bc 100644 --- a/Doc/library/random.rst +++ b/Doc/library/random.rst @@ -49,8 +49,21 @@ from sources provided by the operating system. security purposes. For security or cryptographic uses, see the :mod:`secrets` module. +.. seealso:: -Bookkeeping functions: + M. Matsumoto and T. Nishimura, "Mersenne Twister: A 623-dimensionally + equidistributed uniform pseudorandom number generator", ACM Transactions on + Modeling and Computer Simulation Vol. 8, No. 1, January pp.3-30 1998. + + + `Complementary-Multiply-with-Carry recipe + <https://code.activestate.com/recipes/576707/>`_ for a compatible alternative + random number generator with a long period and comparatively simple update + operations. + + +Bookkeeping functions +--------------------- .. function:: seed(a=None, version=2) @@ -94,7 +107,8 @@ Bookkeeping functions: :meth:`randrange` to handle arbitrarily large ranges. -Functions for integers: +Functions for integers +---------------------- .. function:: randrange(stop) randrange(start, stop[, step]) @@ -117,7 +131,8 @@ Functions for integers: ``randrange(a, b+1)``. -Functions for sequences: +Functions for sequences +----------------------- .. function:: choice(seq) @@ -188,6 +203,9 @@ Functions for sequences: If the sample size is larger than the population size, a :exc:`ValueError` is raised. +Real-valued distributions +------------------------- + The following functions generate specific real-valued distributions. Function parameters are named after the corresponding variables in the distribution's equation, as used in common mathematical practice; most of these equations can @@ -282,7 +300,8 @@ be found in any statistics text. parameter. -Alternative Generator: +Alternative Generator +--------------------- .. class:: SystemRandom([seed]) @@ -294,19 +313,6 @@ Alternative Generator: :exc:`NotImplementedError` if called. -.. seealso:: - - M. Matsumoto and T. Nishimura, "Mersenne Twister: A 623-dimensionally - equidistributed uniform pseudorandom number generator", ACM Transactions on - Modeling and Computer Simulation Vol. 8, No. 1, January pp.3-30 1998. - - - `Complementary-Multiply-with-Carry recipe - <https://code.activestate.com/recipes/576707/>`_ for a compatible alternative - random number generator with a long period and comparatively simple update - operations. - - Notes on Reproducibility ------------------------ @@ -333,13 +339,13 @@ Basic examples:: >>> random() # Random float: 0.0 <= x < 1.0 0.37444887175646646 - >>> uniform(2, 10) # Random float: 2.0 <= x < 10.0 + >>> uniform(2.5, 10.0) # Random float: 2.5 <= x < 10.0 3.1800146073117523 - >>> expovariate(1/5) # Interval between arrivals averaging 5 seconds + >>> expovariate(1 / 5) # Interval between arrivals averaging 5 seconds 5.148957571865031 - >>> randrange(10) # Integer from 0 to 9 + >>> randrange(10) # Integer from 0 to 9 inclusive 7 >>> randrange(0, 101, 2) # Even integer from 0 to 100 inclusive @@ -362,17 +368,16 @@ Simulations:: >>> choices(['red', 'black', 'green'], [18, 18, 2], k=6) ['red', 'green', 'black', 'black', 'red', 'black'] - # Deal 20 cards without replacement from a deck of 52 - # playing cards and determine the proportion of cards - # with a ten-value (i.e. a ten, jack, queen, or king). + # Deal 20 cards without replacement from a deck of 52 playing cards + # and determine the proportion of cards with a ten-value (i.e. a ten, + # jack, queen, or king). >>> deck = collections.Counter(tens=16, low_cards=36) >>> seen = sample(list(deck.elements()), k=20) >>> print(seen.count('tens') / 20) 0.15 - # Estimate the probability of getting 5 or more heads - # from 7 spins of a biased coin that settles on heads - # 60% of the time. + # Estimate the probability of getting 5 or more heads from 7 spins + # of a biased coin that settles on heads 60% of the time. >>> n = 10000 >>> cw = [0.60, 1.00] >>> sum(choices('HT', cum_weights=cw, k=7).count('H') >= 5 for i in range(n)) / n |