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Add documentation for the help() built-in; contributed by Ka-Ping Yee. This is part of SF patch #494622.
author Fred Drake <fdrake@acm.org>
date Tue, 18 Dec 2001 16:31:08 +0000
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1 \section{\module{whrandom} ---
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2 Pseudo-random number generator}
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3
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4 \declaremodule{standard}{whrandom}
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5 \modulesynopsis{Floating point pseudo-random number generator.}
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6
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7 \deprecated{2.1}{Use \refmodule{random} instead.}
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8
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9 \note{This module was an implementation detail of the
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10 \refmodule{random} module in releases of Python prior to 2.1. It is
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11 no longer used. Please do not use this module directly; use
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12 \refmodule{random} instead.}
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13
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14 This module implements a Wichmann-Hill pseudo-random number generator
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15 class that is also named \class{whrandom}. Instances of the
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16 \class{whrandom} class conform to the Random Number Generator
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17 interface described in section \ref{rng-objects}. They also offer the
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18 following method, specific to the Wichmann-Hill algorithm:
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19
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20 \begin{methoddesc}[whrandom]{seed}{\optional{x, y, z}}
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21 Initializes the random number generator from the integers \var{x},
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22 \var{y} and \var{z}. When the module is first imported, the random
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23 number is initialized using values derived from the current time.
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24 If \var{x}, \var{y}, and \var{z} are either omitted or \code{0}, the
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25 seed will be computed from the current system time. If one or two
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26 of the parameters are \code{0}, but not all three, the zero values
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27 are replaced by ones. This causes some apparently different seeds
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28 to be equal, with the corresponding result on the pseudo-random
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29 series produced by the generator.
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30 \end{methoddesc}
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31
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32 \begin{funcdesc}{choice}{seq}
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33 Chooses a random element from the non-empty sequence \var{seq} and returns it.
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34 \end{funcdesc}
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35
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36 \begin{funcdesc}{randint}{a, b}
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37 Returns a random integer \var{N} such that \code{\var{a}<=\var{N}<=\var{b}}.
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38 \end{funcdesc}
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39
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40 \begin{funcdesc}{random}{}
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41 Returns the next random floating point number in the range [0.0 ... 1.0).
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42 \end{funcdesc}
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43
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44 \begin{funcdesc}{seed}{x, y, z}
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45 Initializes the random number generator from the integers \var{x},
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46 \var{y} and \var{z}. When the module is first imported, the random
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47 number is initialized using values derived from the current time.
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48 \end{funcdesc}
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49
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50 \begin{funcdesc}{uniform}{a, b}
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51 Returns a random real number \var{N} such that \code{\var{a}<=\var{N}<\var{b}}.
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52 \end{funcdesc}
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53
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54 When imported, the \module{whrandom} module also creates an instance of
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55 the \class{whrandom} class, and makes the methods of that instance
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56 available at the module level. Therefore one can write either
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57 \code{N = whrandom.random()} or:
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58
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59 \begin{verbatim}
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60 generator = whrandom.whrandom()
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61 N = generator.random()
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62 \end{verbatim}
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63
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64 Note that using separate instances of the generator leads to
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65 independent sequences of pseudo-random numbers.
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66
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67 \begin{seealso}
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68 \seemodule{random}{Generators for various random distributions and
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69 documentation for the Random Number Generator
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70 interface.}
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71 \seetext{Wichmann, B. A. \& Hill, I. D., ``Algorithm AS 183:
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72 An efficient and portable pseudo-random number generator'',
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73 \citetitle{Applied Statistics} 31 (1982) 188-190.}
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74 \end{seealso}