IPython/inprocess/blockingkernelmanager.py

""" Implements a fully blocking kernel manager.

Useful for test suites and blocking terminal interfaces.
"""
#-----------------------------------------------------------------------------
#  Copyright (C) 2012  The IPython Development Team
#
#  Distributed under the terms of the BSD License.  The full license is in
#  the file COPYING.txt, distributed as part of this software.
#-----------------------------------------------------------------------------

#-----------------------------------------------------------------------------
# Imports
#-----------------------------------------------------------------------------
from __future__ import print_function

# Standard library imports.
import Queue
from threading import Event

# Local imports.
from IPython.utils.io import raw_print
from IPython.utils.traitlets import Type
from kernelmanager import InProcessKernelManager, ShellInProcessChannel, \
    SubInProcessChannel, StdInInProcessChannel

#-----------------------------------------------------------------------------
# Utility classes
#-----------------------------------------------------------------------------

class BlockingChannelMixin(object):
    
    def __init__(self, *args, **kwds):
        super(BlockingChannelMixin, self).__init__(*args, **kwds)
        self._in_queue = Queue.Queue()
        
    def call_handlers(self, msg):
        self._in_queue.put(msg)
        
    def get_msg(self, block=True, timeout=None):
        """ Gets a message if there is one that is ready. """
        return self._in_queue.get(block, timeout)
        
    def get_msgs(self):
        """ Get all messages that are currently ready. """
        msgs = []
        while True:
            try:
                msgs.append(self.get_msg(block=False))
            except Queue.Empty:
                break
        return msgs
    
    def msg_ready(self):
        """ Is there a message that has been received? """
        return not self._in_queue.empty()

#-----------------------------------------------------------------------------
# Blocking kernel manager
#-----------------------------------------------------------------------------

class BlockingShellInProcessChannel(BlockingChannelMixin, ShellInProcessChannel):
    pass

class BlockingSubInProcessChannel(BlockingChannelMixin, SubInProcessChannel):
    pass

class BlockingStdInInProcessChannel(BlockingChannelMixin, StdInInProcessChannel):
    
    def call_handlers(self, msg):
        """ Overridden for the in-process channel.

        This methods simply calls raw_input directly.
        """
        msg_type = msg['header']['msg_type']
        if msg_type == 'input_request':
            _raw_input = self.manager.kernel._sys_raw_input
            prompt = msg['content']['prompt']
            raw_print(prompt, end='')
            self.input(_raw_input())

class BlockingInProcessKernelManager(InProcessKernelManager):

    # The classes to use for the various channels.
    shell_channel_class = Type(BlockingShellInProcessChannel)
    sub_channel_class = Type(BlockingSubInProcessChannel)
    stdin_channel_class = Type(BlockingStdInInProcessChannel)