This section provides everything you need to know about using Shout.

Creating a Message

Start by importing the essentials from shout.

from shout import Message, has_ears, hears, shout

Now we can create a new type of Message.

class MyMessage(Message):

Our Message type will allow us to shout() args and kwargs around our application. But, before we can do that…

Who is Listening?

Let’s make a function that can actually hear us shout() our Message s.

@hears(MyMessage, inside="A")
def maximum(msg):
    return upper(msg) + "!!"

maximum() will hear all MyMessage shouts inside room “A”. In this case only one type of Message will be heard, but multiple Message s can be passed as args to hears(). Additionally multiple rooms can be passed as a tuple to the inside keyword argument. If you don’t pass any room names to inside, your function will listen in the default room, “void”.

Does your class have ears?

You’re every day class doesn’t have ears so it’s methods won’t be able to hear any shouted Message s. It’s super simple to give a class ears, just decorate it with has_ears()!

class Volumes(object):

    def low(msg):
        return lower(msg)

    def medium(msg):
        return msg.title()

    def high(msg):
        return upper(msg)

v = Volumes()

Once we’ve given our class ears, the last thing we have to do is create an instance of it. On instantiation the bound methods are added as listeners to the appropriate Message s.

Shout at the top of your lungs!

We’ve got our Message and a bunch of listeners, now we can shout all we want to.

m = shout(MyMessage, "hello there", inside="A")

Now we’ve shouted a Message and we’ve got a Message instance bound to m. Message instances have a bunch of useful attributes.

print "args, kwargs: ", m.args, m.kwargs
print "response: ", m.response
print "success: ", m.success
print "exception: ", m.exc

# args, kwargs: ("hello there", ), {}
# response: ["HELLO THERE!!"]
# success: True
# exception: None

Cool, but, judging from the response, none of our methods in Volumes heard us shout. That’s because we shouted inside room “A”. Let’s see what happens if we shout again but this time, not explicitly passing a room to the inside keyword.

m = shout(MyMessage, "hello again")

print "args, kwargs: ", m.args, m.kwargs
print "response: ", m.response
print "success: ", m.success
print "exception: ", m.exc

# args, kwargs: ("hello again", ), {}
# response: ["hello again", "Hello Again", "HELLO AGAIN"]
# success: True
# exception: None

There we go! This time we’ve shouted inside the default room “void”, reaching all of our Volumes instance’s listeners. It’s important to note that while we only passed one argument in our shouts, any arg, kwarg signature is supported. Message signatures should be set by their listeners. So, if you have multiple listeners for the same type of Message, ensure that they all take the same parameters.


Shout has extensive logging which is turned off by default.

import logging
shout_logger = logging.getLogger('Shout!')

This will set Shouts logger level to logging.DEBUG. Printing out a ton of useful messages! You can also log to a file.