reactor.py

# This is a startup script for IPython. It adds a "line magic" helper that
# makes it very easy to run a Twisted reactor in a separate thread.
#
# This script has been tested in Python 2 and Python 3.
#
# Author: Mike Pontillo <pontillo@gmail.com>
#
# INSTRUCTIONS
# ============
# Place this file in: ~/.ipython/profile_default/startup/reactor.py
#
# USAGE
# =====
# To get a running reactor, assign it to %reactor. When you exit IPython, the
# reactor will be stopped automatically. For example:
#
# In [1]: reactor = %reactor
# Starting reactor...
#
# In [2]: from twisted.names.client import getResolver
#
# In [3]: resolver = getResolver()
#
# In [4]: from pprint import pprint
#
# In [5]: resolver.lookupAddress("launchpad.net").addBoth(lambda data: pprint([rr.payload for rr in data[0]]))
# Out[5]: <Deferred at 0x7f190e0997f0 waiting on Deferred at 0x7f190e0b4278>
# [<A address=91.189.89.223 ttl=351>, <A address=91.189.89.222 ttl=351>]
# 
# In [6]: ^D
# Do you really want to exit ([y]/n)? y
# Reactor stopped.

from IPython.core.magic import (
    Magics,
    magics_class,
    line_magic,
)

@magics_class
class ReactorMagic(Magics):

    def __init__(self, shell=None, *args, **kwargs):
        super(ReactorMagic, self).__init__(shell=shell, *args, **kwargs)
        self.reactor = None
        # Note: I couldn't figure out how to both use atexit.register() here
        # and allow the reactor to cleanly shut down, so we're using this
        # deprecated hook.
        shell.set_hook('shutdown_hook', self.shutdown, _warn_deprecated=False)

    def shutdown(self, *args, **kwargs):
        if self.reactor is not None:
            self.reactor.callFromThread(self.reactor.stop)

    @line_magic
    def reactor(self, line):
        if self.reactor is None:
            import sys
            import twisted.internet.reactor
            self.reactor = twisted.internet.reactor
            self.reactor.addSystemEventTrigger(
                "after", "shutdown", sys.stderr.write, "Reactor stopped.\n")
            self.reactor.addSystemEventTrigger(
                "before", "startup", sys.stderr.write, "Starting reactor...\n")
            from threading import Thread
            t = Thread(target=self.reactor.run, args=(False,))
            t.daemon = True
            t.start()
        return self.reactor

get_ipython().register_magics(ReactorMagic)