In many situations, we need to run some tasks automatically in software. Like, sending an automatic email or doing something specific automatically after a definite interval. These are called scheduled tasks.
Today we will see how to implement scheduled tasks in Django. There are many ways to do it. Like using Celery or using python packages like django-cronjob, django-background-tasks, etc.
Here we will use django-background-tasks. It is very lightweight and easy to use.
A Serializer takes a data that exists on the server, parses data from complex types into a format (JSON or XML) that can be read by other technologies.
Or,
A serializer is a framework that allows complex data such as 'querysets' and model instances to be converted to native Python data types. Then, we can easily render these into JSON, XML, or other content types.
There Two types of Serializers in Django.
The Serializers and ModelSerializers work in a way similar to Forms and ModelForms. Unlike forms, they are not constrained to dealing with HTML output and form encoded input.
We will discuss both types.
The pagination system is one of the most common features of a modern web application like blogs, search engines, a list of results, etc. It gives a better experience to the users.
Seeing the popularity, Django came up with built-in pagination classes for paginating data of an application.
In this article, we will discuss the pagination process with class-based views and function-based views in Django.
We have a model named 'Person'. We created some objects of that model. Till now we were showing all the objects of our model on the same page. Now we will use pagination on our page.
We are familiar with signals & we see much usage of different types of signals. Suppose your friends and you are having fun in your classroom. You assigned one of your friends as an informer who will give you a signal if he sees a teacher coming.
In programming, signals are callables which are called before/after an event.
Middleware is a framework of hooks which works as a ‘plugin’ between Django’s request/response processing. In other words a middleware is a callable that takes a request and returns a response just like a view. Each middleware component is responsible for doing some specific task.
In simple word middlewares are Mediators between client & view.
Let me clear the concept with an example:
Suppose you want to send a letter to your best friend through a post office. You completed the letter & went to post office, but post master told you that you didn't follow the perfect rules to send a letter. Then you corrected it. After that the postmaster received it & sent it to the post office nearer to your friends home. A postman will take the letter from there & deliver it to your friends home. Here, a problem can be happened too. If you make mistake in writing the address then it won't be possible to deliver. But if everything is okey the letter will be delivered on time. Then by following the same procedure your friend can send you a response.
Files used for making beautiful user interface, interactive user experience and functional web pages are called static files. They do not change when a application is running. They aren’t dynamically generated by Python web server. Most common static-files in a typical web application are the following types:
Static files are important for a Django project because the modern web requires more than dynamically generated HTML markup. Let’s see how to configure an application to serve static files. After that we will work with some examples.
A cookie is a small piece of text file that contains data. The data in the cookie is often a random key or token. The server use a cookie to identify a client. Specific cookie known as HTTP cookie is used to identify a specific user and to keep track of that user's movements within the site.
Suppose, you have visited a shop for the first time & bought some cloths of your favorite color. The owner has given you a membership card. Now, if you go again, he might not remember your face but he will recognize the card issued by his shop & can find your buying history & can serve you well. Here, the shop is the web server, you are the client and the membership card is the cookie. As the membership card will not be valid for other shops similarly a cookie won’t be valid for a different website.
Communication between web browsers (clients) and servers is completed via HTTP( Hyper Text Transfer Protocol). It is a stateless protocol. This means a HTTP server does not keep track of any state information. The server will not remember whether a client has visited it before. Each time a client visits the server behaves with it as a new client. The sessions make a stateless protocol stateful.
Django has a session framework which handles cookies. In cookies we store session_key. It is a unique 32-character-long random string. A session_key can be considered as a token (a sequence of characters). It identifies a unique session within a particular web application. Sessions are used to abstract the receiving and sending of cookies, data is saved on server-side, and a session_key is stored in the client-side cookie for identification.
We have already discussed Django Template Tags. In this tutorial, we will work with Django Custom Template Filter.
A template filter is simply a feature that can transform the value of a template variable before it is displayed.
Syntax
{{ variable_name | filter_name }}
There are some inbuilt filters in Django. Let's see some of them first.
To convert the value of a variable into lower case characters:
{{ variable | lower }}
If value is “Bangladesh”, the output will be “bangladesh”.
In this tutorial, we'll discuss 'how to allow users to log in to a website with their own accounts and how to allow them to create accounts. The mechanisms work behind the scene is called authentication.
Authentication verifies a user if he is who he pretends to be, and authorization determines what an authenticated user can do.
Django by default has a user authentication system. It handles user accounts, groups, permissions and cookie-based user sessions. We will discuss the following topics here:
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