Django Current

Recently I wanted a simple solution to track whether a user is online on a given Django site.  The definition of "online" on a site is kind of ambiguous, so I'll define that a user is considered to be online if they have made any request to the site in the last five minutes. I found that one approach is to use Django's caching framework to track when a user last accessed the site.  For example, upon each request, I can have a middleware set the current time as a cache value associated with a given user.  This allows us to store some basic information about logged-in user's online state without having to hit the database on each request and easily retrieve it by accessing the cache. My approach below.  Comments welcome. In settings.py: # add the middleware that you are about to create to settings MIDDLEWARE_CLASSES = ( .... 'middleware.activeuser_middleware.ActiveUserMiddleware' , .... ) # Setup caching per Django docs. In actuality, you...

In a previous post , I wrote about a way to keep track of user permissions on a model instance.  For example, I suggested that each model have a permissions subclass that could be instantiated with a user instance passed as a constructor argument.  Methods on that permissions class could then be called to determine if that user has permission to perform various actions. I also suggested that the threadlocals module could then be used to pass in the user instance to the permissions object in the Django template.  However, from various readings, I get the impression that threadlocals may not be the best thing for passing arguments in a template function.   Therefore, I decided to use a more traditional route of creating a template tag to do something similar. I created a template tag that lets you surround a block of HTML code to hide or show the contents based on the return value of the permission function.  The tag below basically says, "if the logged in use...

Logging is always one of those things that seems like there is a lot of boilerplate code that I tend to always have to lookup oneline each time.  Though logging is very customizable, most of the time I need simply to only need log to a file or files.   Therefore, I'm writing this in hopes of compling a simple configuration that can be dropped into a project.  My understanding is still rudimentary so feel free to drop a comment. A logging framework is built into Django 1.3 which makes it easier to integrate into a given project.  The logging framework contains three main components: formatters, handlers, and loggers.  Formatters determine how the output will be displayed when it is logged.  Handlers handle where output is logged, whether that be a file, the counsole, or an email.  Loggers are associated with handlers and are the objects that one interacts with when logging something.  As in the example below, more than one formatter, hand...

One nice convenience would be to have a way to call manage.py from anywhere within a virtual environment.  For example, if I want to execute 'manage.py shell', it would be nice to be able to execute that from anywhere rather than having to change directory to where manage.py lives. We can already run management commands from anywhere using django-admin by utilizing the --settings flag, but doing this requires a lot of typing. And wrapping the django-admin in a shell script seems inelegant somehow. Instead, I wrote a small python script based off of manage.py.  This can be placed in the ./bin directory in the virtualenv.  The  DjangoManageSettings  object is meant to be customized on a per project basis, and I intend to make it so it can be passed in from a file configuration somewhere. Anyway, thought I would share.  I'm curious to see other approaches to this. # ---------- ${VIRTUAL_ENV}/bin/django_manage.py -------------------------...

One thing I've been experimenting with is model Mixins.  For example, the aim is to create small abstract classes that are each focused around a particular function.  These abstract classes can then be added to arbitrary models to apply those functions to models as desired. For example, say I define a RatingsFields abstract class and a TrackingFields abstract class.  These abstract classes can be mixed into any other model that we wish to add rating or tracking functionality to. core/mixins.py from djangoratings.fields import RatingField # 3rd party module class RatingFields(models.Model): rating = RatingField( range =5) # 5 possible rating values, 1-5 class Meta: abstract = True class TrackingFields(models.Model): deleted_on = models.DateTimeField(blank= True , null= True ) created = models.DateTimeField(auto_now_add= True ) modified = models.DateTimeField(auto_now= True ) class Meta: abstract = True...

Sometimes it's nice to be able to add custom code to the save method of objects in the Django Admin.  So, when editing an object on the Admin object detail page (change form), adding the following method override to your ModelAdmin in admin.py will allow you to add custom code to the save function. In admin.py:   class MyModelAdmin(admin.ModelAdmin): def save_model(self, request, obj, form, change): # custom stuff here obj.save() This is documented in the Django Docs , but I found it particularly useful.

In my last post , I discussed how you can use a simple UserMessage class in your views to report simple error messages.   This way, you can keep track of errors and report them to the users in a clean fashion. One thing I didn't expand upon much is how to create some manager methods to cleanly lookup model instances and report any errors to the UserMessage class.  I think this approach is a little nicer than catching exceptions all over the place, because you don't have to clutter your views with try/catch blocks. In the example below, we create a custom manager that looks up a model instance of "MyModel" with the given hash.  If the selected instance of "MyModel" does not exist or if some other error occurs, it writes an error message to "message" instance passed into it.  You can customize this as you see fit.  For example, in the code below, I pass in a "user" instance that can be used to check permissions in this method.  class ...