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select.select(): Add note that though this function accepts empty lists,

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using *only* empty lists may not be acceptable on all
                  platforms, with the specific caveat that it does not
                  work on Windows.  Also clarified list of acceptable
                  objects that may be in the lists, to let the user know
                  that file objects are not usable here on Windows.
This commit is contained in:
Fred Drake 2000-12-11 15:50:07 +00:00
parent f7d5aa61d3
commit 5255c791cc
1 changed files with 15 additions and 13 deletions
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28
Doc/lib/libselect.tex
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@ -33,14 +33,16 @@ polling objects.
\begin{funcdesc}{select}{iwtd, owtd, ewtd\optional{, timeout}}
This is a straightforward interface to the \UNIX{} \cfunction{select()}
system call. The first three arguments are lists of `waitable
objects': either integers representing \UNIX{} file descriptors or
objects': either integers representing file descriptors or
objects with a parameterless method named \method{fileno()} returning
such an integer. The three lists of waitable objects are for input,
output and `exceptional conditions', respectively. Empty lists are
allowed. The optional \var{timeout} argument specifies a time-out as a
floating point number in seconds. When the \var{timeout} argument
is omitted the function blocks until at least one file descriptor is
ready. A time-out value of zero specifies a poll and never blocks.
allowed, but acceptance of three empty lists is platform-dependent.
(It is known to work on \UNIX{} but not on Windows.) The optional
\var{timeout} argument specifies a time-out as a floating point number
in seconds. When the \var{timeout} argument is omitted the function
blocks until at least one file descriptor is ready. A time-out value
of zero specifies a poll and never blocks.
The return value is a triple of lists of objects that are ready:
subsets of the first three arguments. When the time-out is reached
@ -52,14 +54,14 @@ objects (e.g. \code{sys.stdin}, or objects returned by
\function{open()} or \function{os.popen()}), socket objects
returned by \function{socket.socket()},%
\withsubitem{(in module socket)}{\ttindex{socket()}}
\withsubitem{(in module os)}{\ttindex{popen()}}
and the module \module{stdwin}\refbimodindex{stdwin} which happens to
define a function
\function{fileno()}\withsubitem{(in module stdwin)}{\ttindex{fileno()}}
for just this purpose. You may
also define a \dfn{wrapper} class yourself, as long as it has an
appropriate \method{fileno()} method (that really returns a \UNIX{}
file descriptor, not just a random integer).
\withsubitem{(in module os)}{\ttindex{popen()}}.
You may also define a \dfn{wrapper} class yourself, as long as it has
an appropriate \method{fileno()} method (that really returns a file
descriptor, not just a random integer).
\strong{Note:}\index{WinSock} File objects on Windows are not
acceptable, but sockets are. On Windows, the underlying
\cfunction{select()} function is provided by the WinSock library, and
does not handle file desciptors that don't originate from WinSock.
\end{funcdesc}
\subsection{Polling Objects