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:mod:`select` -- wait for events on a set of streams
========================================================================
.. module:: select
:synopsis: wait for events on a set of streams
This module provides functions to wait for events on streams (select streams
which are ready for operations).
Pyboard specifics
-----------------
Polling is an efficient way of waiting for read/write activity on multiple
objects. Current objects that support polling are: :class:`pyb.UART`,
:class:`pyb.USB_VCP`.
Functions
---------
.. function:: poll()
Create an instance of the Poll class.
.. function:: select(rlist, wlist, xlist[, timeout])
Wait for activity on a set of objects.
This function is provided for compatibility and is not efficient. Usage
of :class:`Poll` is recommended instead.
.. _class: Poll
class ``Poll``
--------------
Methods
~~~~~~~
.. method:: poll.register(obj[, eventmask])
Register ``obj`` for polling. ``eventmask`` is logical OR of:
* ``select.POLLIN`` - data available for reading
* ``select.POLLOUT`` - more data can be written
* ``select.POLLERR`` - error occurred
* ``select.POLLHUP`` - end of stream/connection termination detected
``eventmask`` defaults to ``select.POLLIN | select.POLLOUT``.
.. method:: poll.unregister(obj)
Unregister ``obj`` from polling.
.. method:: poll.modify(obj, eventmask)
Modify the ``eventmask`` for ``obj``.
.. method:: poll.poll([timeout])
Wait for at least one of the registered objects to become ready. Returns
list of (``obj``, ``event``, ...) tuples, ``event`` element specifies
which events happened with a stream and is a combination of `select.POLL*`
constants described above. There may be other elements in tuple, depending
on a platform and version, so don't assume that its size is 2. In case of
timeout, an empty list is returned.
Timeout is in milliseconds.
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