environment/share/doc/ipython/examples/parallel/iopubwatcher.py
def main(connection_file):
    """watch iopub channel, and print messages"""
    
    ctx = zmq.Context.instance()
    
    with open(connection_file) as f:
        cfg = json.loads(f.read())
    
    location = cfg['location']
    reg_url = cfg['url']
    session = Session(key=str_to_bytes(cfg['exec_key']))
    
    query = ctx.socket(zmq.DEALER)
    query.connect(disambiguate_url(cfg['url'], location))
    session.send(query, "connection_request")
    idents,msg = session.recv(query, mode=0)
    c = msg['content']
    iopub_url = disambiguate_url(c['iopub'], location)
    sub = ctx.socket(zmq.SUB)
    # This will subscribe to all messages:
    sub.setsockopt(zmq.SUBSCRIBE, b'')
    # replace with b'' with b'engine.1.stdout' to subscribe only to engine 1's stdout
    # 0MQ subscriptions are simple 'foo*' matches, so 'engine.1.' subscribes
    # to everything from engine 1, but there is no way to subscribe to
    # just stdout from everyone.
    # multiple calls to subscribe will add subscriptions, e.g. to subscribe to
    # engine 1's stderr and engine 2's stdout:
    # sub.setsockopt(zmq.SUBSCRIBE, b'engine.1.stderr')
    # sub.setsockopt(zmq.SUBSCRIBE, b'engine.2.stdout')
    sub.connect(iopub_url)
    while True:
        try:
            idents,msg = session.recv(sub, mode=0)
        except KeyboardInterrupt:
            return
        # ident always length 1 here
        topic = idents[0]
        if msg['msg_type'] == 'stream':
            # stdout/stderr
            # stream names are in msg['content']['name'], if you want to handle
            # them differently
            print("%s: %s" % (topic, msg['content']['data']))
        elif msg['msg_type'] == 'pyerr':
            # Python traceback
            c = msg['content']
            print(topic + ':')
            for line in c['traceback']:
                # indent lines
                print('    ' + line)
def main(connection_file):
    """watch iopub channel, and print messages"""
    
    ctx = zmq.Context.instance()
    
    with open(connection_file) as f:
        cfg = json.loads(f.read())
    
    location = cfg['location']
    reg_url = cfg['url']
    session = Session(key=str_to_bytes(cfg['exec_key']))
    
    query = ctx.socket(zmq.DEALER)
    query.connect(disambiguate_url(cfg['url'], location))
    session.send(query, "connection_request")
    idents,msg = session.recv(query, mode=0)
    c = msg['content']
    iopub_url = disambiguate_url(c['iopub'], location)
    sub = ctx.socket(zmq.SUB)
    # This will subscribe to all messages:
    sub.setsockopt(zmq.SUBSCRIBE, b'')
    # replace with b'' with b'engine.1.stdout' to subscribe only to engine 1's stdout
    # 0MQ subscriptions are simple 'foo*' matches, so 'engine.1.' subscribes
    # to everything from engine 1, but there is no way to subscribe to
    # just stdout from everyone.
    # multiple calls to subscribe will add subscriptions, e.g. to subscribe to
    # engine 1's stderr and engine 2's stdout:
    # sub.setsockopt(zmq.SUBSCRIBE, b'engine.1.stderr')
    # sub.setsockopt(zmq.SUBSCRIBE, b'engine.2.stdout')
    sub.connect(iopub_url)
    while True:
        try:
            idents,msg = session.recv(sub, mode=0)
        except KeyboardInterrupt:
            return
        # ident always length 1 here
        topic = idents[0]
        if msg['msg_type'] == 'stream':
            # stdout/stderr
            # stream names are in msg['content']['name'], if you want to handle
            # them differently
            print("%s: %s" % (topic, msg['content']['data']))
        elif msg['msg_type'] == 'pyerr':
            # Python traceback
            c = msg['content']
            print(topic + ':')
            for line in c['traceback']:
                # indent lines
                print('    ' + line)
watch iopub channel, and print messages