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<title>5.10 whrandom -- Pseudo-random number generator</title>
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<H1><A NAME="SECTION0071000000000000000000">
5.10 <tt class="module">whrandom</tt> --
         Pseudo-random number generator</A>
</H1>

<P>
<A NAME="module-whrandom"></A>

<P>
<div class="versionnote"><b>Deprecated since release 2.1.</b>
Use <tt class="module"><a href="module-random.html">random</a></tt> instead.</div><p></p>

<P>
<span class="note"><b class="label">Note:</b>
This module was an implementation detail of the
<tt class="module"><a href="module-random.html">random</a></tt> module in releases of Python prior to 2.1.  It is
no longer used.  Please do not use this module directly; use
<tt class="module"><a href="module-random.html">random</a></tt> instead.</span>

<P>
This module implements a Wichmann-Hill pseudo-random number generator
class that is also named <tt class="class">whrandom</tt>.  Instances of the
<tt class="class">whrandom</tt> class conform to the Random Number Generator
interface described in the docs for the <tt class="module"><a href="module-random.html">random</a></tt> module.
They also offer the
following method, specific to the Wichmann-Hill algorithm:

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1323' xml:id='l2h-1323' class="method">seed</tt></b>(</nobr></td>
  <td><var></var><big>[</big><var>x, y, z</var><big>]</big><var></var>)</td></tr></table></dt>
<dd>
  Initializes the random number generator from the integers <var>x</var>,
  <var>y</var> and <var>z</var>.  When the module is first imported, the random
  number is initialized using values derived from the current time.
  If <var>x</var>, <var>y</var>, and <var>z</var> are either omitted or <code>0</code>, the
  seed will be computed from the current system time.  If one or two
  of the parameters are <code>0</code>, but not all three, the zero values
  are replaced by ones.  This causes some apparently different seeds
  to be equal, with the corresponding result on the pseudo-random
  series produced by the generator.
</dl>

<P>
Other supported methods include:

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1324' xml:id='l2h-1324' class="function">choice</tt></b>(</nobr></td>
  <td><var>seq</var>)</td></tr></table></dt>
<dd>
Chooses a random element from the non-empty sequence <var>seq</var> and returns it.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1325' xml:id='l2h-1325' class="function">randint</tt></b>(</nobr></td>
  <td><var>a, b</var>)</td></tr></table></dt>
<dd>
Returns a random integer <var>N</var> such that <code><var>a</var>&lt;=<var>N</var>&lt;=<var>b</var></code>.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1326' xml:id='l2h-1326' class="function">random</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
Returns the next random floating point number in the range [0.0 ... 1.0).
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1327' xml:id='l2h-1327' class="function">seed</tt></b>(</nobr></td>
  <td><var>x, y, z</var>)</td></tr></table></dt>
<dd>
Initializes the random number generator from the integers <var>x</var>,
<var>y</var> and <var>z</var>.  When the module is first imported, the random
number is initialized using values derived from the current time.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-1328' xml:id='l2h-1328' class="function">uniform</tt></b>(</nobr></td>
  <td><var>a, b</var>)</td></tr></table></dt>
<dd>
Returns a random real number <var>N</var> such that <code><var>a</var>&lt;=<var>N</var>&lt;<var>b</var></code>.
</dl>

<P>
When imported, the <tt class="module">whrandom</tt> module also creates an instance of
the <tt class="class">whrandom</tt> class, and makes the methods of that instance
available at the module level.  Therefore one can write either
<code>N = whrandom.random()</code> or:

<P>
<div class="verbatim"><pre>
generator = whrandom.whrandom()
N = generator.random()
</pre></div>

<P>
Note that using separate instances of the generator leads to
independent sequences of pseudo-random numbers.

<P>
<div class="seealso">
  <p class="heading">See Also:</p>

  <dl compact="compact" class="seemodule">
    <dt>Module <b><tt class="module"><a href="module-random.html">random</a></tt>:</b>
    <dd>Generators for various random distributions and
                     documentation for the Random Number Generator
                     interface.
  </dl>
  <div class="seetext"><p>Wichmann, B. A. &amp; Hill, I. D., ``Algorithm AS 183:
           An efficient and portable pseudo-random number generator'',
           <em class="citetitle"
 >Applied Statistics</em> 31 (1982) 188-190.</p></div>
</div>

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<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
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