Given a pair of pipes with a python process at each end, this module
allows one end to make calls on the other. This is used by the su module
to allow control of a subprocess running as another user, but it may also
be useful in other situations. The caller end should use the master_proxy
- select(rlist, wlist, xlist[, timeout]) -> (rlist, wlist, xlist)
Wait until one or more file descriptors are ready for some kind of I/O.
The first three arguments are lists of file descriptors to be waited for:
rlist -- wait until ready for reading
wlist -- wait until ready for writing
xlist -- wait for an ``exceptional condition''
If only one kind of condition is required, pass  for the other lists.
A file descriptor is either a socket or file object, or a small integer
gotten from a fileno() method call on one of those.
The optional 4th argument specifies a timeout in seconds; it may be
a floating point number to specify fractions of seconds. If it is absent
or None, the call will never time out.
The return value is a tuple of three lists corresponding to the first three
arguments; each contains the subset of the corresponding file descriptors
that are ready.
*** IMPORTANT NOTICE ***
On Windows, only sockets are supported; on Unix, all file descriptors.