Django, display count of unread messages in base template

I am working on a project in which I have implemented messaging system like facebook where users can send messages to each other. The number of unread messages of a particular thread is also displayed on the messages page.

Now what I want is to display the count of unread messages in the navigation bar (which is there in base.html) each time user logs in. How to do this whenever a user logs in?

Please suggest, and I don't want to use any other app for this purpose. Thanks

You can write a simple tag which can do this for you.

def unread_messages(user):
    return user.messages_set.filter(read=False).count()
    #replace the messages_set with the appropriate related_name, and also the filter field. (I am assuming it to be "read")

register.simple_tag(unread_messages)

and in the base template:

{% load <yourtemplatetagname> %}

{% if request.user.is_authenticated %}
    {{ request.user|unread_messages }}
{% endif %}