Is there a way to access the context from everywhere in Django?

Question

I'm looking for a way to have a global variable that is accessible by any module within my django request without having to pass it around as parameter. Traditionally in other MVCs, I would store it in the request context or session and access the context with something like a "get_current_context" method (which I couldn't find in Django).

Is there something like this, or some other mechanism that will allow me to have a value available from anywhere in the request context?

TIA!

UPDATE: My research has only come up with one viable solution - thread locals (some would argue it's not viable, but there's a pretty active discussion about it, with pros and cons and seems like most people think you should be able to use it in Django, if you do it responsibly).

Answer 1

It's still not completely clear to me what you're trying to achieve, but it sounds like you might want something like the following.

If you create a piece of middleware in, say...

myproject/myapp/middleware/globalrequestmiddleware.py

...which looks like this...

import thread

class GlobalRequestMiddleware(object):
    _threadmap = {}

    @classmethod
    def get_current_request(cls):
        return cls._threadmap[thread.get_ident()]

    def process_request(self, request):
        self._threadmap[thread.get_ident()] = request

    def process_exception(self, request, exception):
        try:
            del self._threadmap[thread.get_ident()]
        except KeyError:
            pass

    def process_response(self, request, response):
        try:
            del self._threadmap[thread.get_ident()]
        except KeyError:
            pass
        return response

...then add it into your settings.py MIDDLEWARE_CLASSES as the first item in the list...

MIDDLEWARE_CLASSES = (
    'myproject.myapp.middleware.globalrequestmiddleware.GlobalRequestMiddleware',
    # ...
)

...then you can use it anywhere in the request/response process like this...

from myproject.myapp.middleware.globalrequestmiddleware import GlobalRequestMiddleware

# Get the current request object for this thread
request = GlobalRequestMiddleware.get_current_request()

# Access some of its attributes
print 'The current value of session variable "foo" is "%s"' % request.SESSION['foo']
print 'The current user is "%s"' % request.user.username

# Add something to it, which we can use later on
request.some_new_attr = 'some_new_value'

...or whatever it is you want to do.

Answer 2

You have to write your own ContextProcessor, like explained here.

---

EDIT:

After you've created a Context Processor, e.g.,

def ip_address_processor(request):
  return {'ip_address': request.META['REMOTE_ADDR']}

you can get the variables you need by initializing a RequestContext, like this:

from django.template import RequestContext

def myview(request):
  rc = RequestContext(request)
  rc.get('ip_address')

However, please note that if you don't put your Context Processor inside the TEMPLATE_CONTEXT_PROCESSORS tuple, you have to pass the processor to RequestContext as an argument, e.g.:

from django.template import RequestContext

def ip_address_processor(request):
  return {'ip_address': request.META['REMOTE_ADDR']}

def myview(request):
  rc = RequestContext(request, processors=[ip_address_processor])
  rc.get('ip_address')

Some useful links:

• Django Template API documentation
• Settings TEMPLATE_CONTEXT_PROCESSORS
• Django Book: Advanced Templates