Rivalry2

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Original 2026-01-01

Modified 2026-02-21

1 In this lesson, you'll learn what components make up the backend when written in Python. We'll get acquainted with the key terms we'll need for the course.

2 <h2>Web servers</h2>

3 Most web applications rely on the client-server model:

4 <ul><li>Client: The user opens the browser and sends a request</li>

5 <li>Server: The request from the browser goes tothe web server, which begins to process it</li>

6 </ul>Some languages embed the web server directly into the application, but most interpreted languages use an external program. There are several standalone web servers, but the most popular isNginx. It handles incoming requests, serves static files, and distributes requests to web applications.

7 <h2>WSGI</h2>

8 If the web application backend runs on Python, we usually find aWSGI serverrunningWSGI applicationsbehind the web server. Let's take a closer look at what that is.

9 TheWSGI(Web Server Gateway Interface) is the abstraction under which the requests get answered. It is a Python function that takes a request and returns a response. The basic WSGI application looks like this:

10 Let's take a closer look at this snippet of code:

11 <ol><li>Everything about a particular query comes in the environ argument</li>

12 <li>The `start_response' function sets the response parameters - its size and content type</li>

13 <li>The function returns an iterator that returns the response line by line</li>

14 </ol>The web application is easy to create:

15 <ul><li>Use the popular WSGI server<a>gunicorn</a></li>

16 <li>Put the function in the example.py file</li>

17 <li>Run the command gunicorn -w 4 example:app</li>

18 </ul><h2>Web Framework</h2>

19 Above, we saw a simple web application. Even though it works, it'll return identical text for every query. Writing something more complex in this style would be problematic, though doable. To make a backend developer's life easier and to help them implement typical applications, we useframeworks- libraries that define a ready-made application structure.

20 The developer only needs to insert his code snippets into this structure, and the application structure is ready to use. The most popular web frameworks for Python areDjangoandFlask.

21 Web frameworks can do many different things:

22 <ul><li>Perform routing</li>

23 <li>Simplify work with headers and query data</li>

24 <li>Form responses in various formats</li>

25 <li>Store query histories in files for statistics and debugging</li>

26 - </ul>What else is in the backend besides query processing? Most of the time, there are two tools:

26 + </ul><h2>ORM and Templating Tool</h2>

27 + What else is in the backend besides query processing? Most of the time, there are two tools:

27 <ul><li>ORM(Object-Relational Mapping) is a tool for working with records in databases. It represents records as objects that are understandable by Python</li>

28 <ul><li>ORM(Object-Relational Mapping) is a tool for working with records in databases. It represents records as objects that are understandable by Python</li>

28 <li>Templatingis a tool that allows you to write HTML and CSS in separate files and modify their contents. It allows you to create a layout once and then programmatically retrieve different pages from the layout</li>

29 <li>Templatingis a tool that allows you to write HTML and CSS in separate files and modify their contents. It allows you to create a layout once and then programmatically retrieve different pages from the layout</li>

29 </ul>Django and some other web frameworks already include an ORM and templating engine.

30 </ul>Django and some other web frameworks already include an ORM and templating engine.