Reworked random.py so that it no longer depends on, and offers all the

functionality of, whrandom.py.  Also closes all the "XXX" todos in
random.py.  New frequently-requested functions/methods getstate() and
setstate().  All exported functions are now bound methods of a hidden
instance.  Killed all unintended exports.  Updated the docs.
FRED:  The more I fiddle the docs, the less I understand the exact
intended use of the \var, \code, \method tags.  Please review critically.
GUIDO:  See email.  I updated NEWS as if whrandom were deprecated; I
think it should be.
This commit is contained in:
Tim Peters 2001-01-25 03:36:26 +00:00
parent 83125775e0
commit d7b5e88e8e
3 changed files with 501 additions and 308 deletions

View file

@ -32,6 +32,18 @@ functions from multiple threads, you should explicitly serialize the calls.
Else, because no critical sections are implemented internally, calls
from different threads may see the same return values.
The functions supplied by this module are actually bound methods of a
hidden instance of the \var{random.Random} class. You can instantiate
your own instances of \var{Random} to get generators that don't share state.
This may be especially useful for multi-threaded programs, although there's
no simple way to seed the distinct generators to ensure that the generated
sequences won't overlap. Class \var{Random} can also be subclassed if you
want to use a different basic generator of your own devising: in that
case, override the \method{random()}, \method{seed()}, \method{getstate()}
and \method{setstate()} methods.
Bookkeeping functions:
\begin{funcdesc}{seed}{\optional{x}}
Initialize the basic random number generator.
@ -45,15 +57,19 @@ from different threads may see the same return values.
the module is first imported.
\end{funcdesc}
\begin{funcdesc}{choice}{seq}
Return a random element from the non-empty sequence \var{seq}.
\end{funcdesc}
\begin{funcdesc}{getstate}{}
Return an object capturing the current internal state of the generator.
This object can be passed to \code{setstate()} to restore the state.
\end{funcdesc}
\begin{funcdesc}{randint}{a, b}
\deprecated{2.0}{Use \function{randrange()} instead.}
Return a random integer \var{N} such that
\code{\var{a} <= \var{N} <= \var{b}}.
\end{funcdesc}
\begin{funcdesc}{setstate}{state}
\var{state} should have been obtained from a previous call to
\code{getstate()}, and \code{setstate()} restores the internal state
of the generate to what it was at the time \code{setstate()} was called.
\end{funcdesc}
Functions for integers:
\begin{funcdesc}{randrange}{\optional{start,} stop\optional{, step}}
Return a randomly selected element from \code{range(\var{start},
@ -63,6 +79,37 @@ from different threads may see the same return values.
\versionadded{1.5.2}
\end{funcdesc}
\begin{funcdesc}{randint}{a, b}
\deprecated{2.0}{Use \function{randrange()} instead.}
Return a random integer \var{N} such that
\code{\var{a} <= \var{N} <= \var{b}}.
\end{funcdesc}
Functions for sequences:
\begin{funcdesc}{choice}{seq}
Return a random element from the non-empty sequence \var{seq}.
\end{funcdesc}
\begin{funcdesc}{shuffle}{x\optional{, random}}
Shuffle the sequence \var{x} in place.
The optional argument \var{random} is a 0-argument function
returning a random float in [0.0, 1.0); by default, this is the
function \function{random()}.
Note that for even rather small \code{len(\var{x})}, the total
number of permutations of \var{x} is larger than the period of most
random number generators; this implies that most permutations of a
long sequence can never be generated.
\end{funcdesc}
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 be found in any statistics text.
\begin{funcdesc}{random}{}
Return the next random floating point number in the range [0.0, 1.0).
\end{funcdesc}
@ -72,14 +119,6 @@ from different threads may see the same return values.
\code{\var{a} <= \var{N} < \var{b}}.
\end{funcdesc}
The following functions are defined to support specific distributions,
and all return real values. Function parameters are named after the
corresponding variables in the distribution's equation, as used in
common mathematical practice; most of these equations can be found in
any statistics text.
\begin{funcdesc}{betavariate}{alpha, beta}
Beta distribution. Conditions on the parameters are
\code{\var{alpha} > -1} and \code{\var{beta} > -1}.
@ -143,21 +182,6 @@ any statistics text.
\end{funcdesc}
This function does not represent a specific distribution, but
implements a standard useful algorithm:
\begin{funcdesc}{shuffle}{x\optional{, random}}
Shuffle the sequence \var{x} in place.
The optional argument \var{random} is a 0-argument function
returning a random float in [0.0, 1.0); by default, this is the
function \function{random()}.
Note that for even rather small \code{len(\var{x})}, the total
number of permutations of \var{x} is larger than the period of most
random number generators; this implies that most permutations of a
long sequence can never be generated.
\end{funcdesc}
\begin{seealso}
\seetext{Wichmann, B. A. \& Hill, I. D., ``Algorithm AS 183:
An efficient and portable pseudo-random number generator'',