2021_05_10_WebClass-5

Web Development Class - V

Web Development Class - V recording: Here

May 10, 2021

Client-Server architecture

What is Client?

• Anything requesting for some resource is a client.
• Example - Browser, Mobile-App, Tools like Postman.

What is Server?

• Anything responding to request by providing reasources is a Server.
• Example - Your PC (When Running a Local Server), Dedicated Hardware (Used by Companies for hosting Some Data e.g. Websites),

What is Web Server?

• It is a Server that responds to client's request by providing reasources in the form of HTML file, CSS file, JS file or, images, etc.

What is Web Server Software?

• It is program running on the Server Hardware which handles the request-response process.
• Example - Apache, Nginx etc.
• The primary task of these programs is to respond to client requests by processing your backend code.
• Client Side and Server Side are two different things.
• Both are not connected in any way but interact to each other using Request-Response method.
• Generally Client sends request to server and server responds accordingly.
• Server can not send any data to client until it asks server to respond.
• Different protocols(http, https, ftp, ws etc) are followed to establish communication between client and server.

Types of Responses Sent by Web Server

• Static Response - Directly Available in to Web-Server in a Static Storage Device e.g. Hard-Disk.
• Dynamic Response - Response have to be generated by first fetching some data from the Database and then using it inside the Response which is to be sent.

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Django Web Framework

What is Django?

• Django is a web development framework.
• It helps in building and maintaining quality web applications.
• Django helps eliminate repetitive tasks making the development process an easy and time saving experience.
• Some popular websites built using Django are - Instagram, Pinterest, Disqus, Spotify, Youtube, etc.

Library vs Framework

• When we use a library, we are in charge of the application flow.
• We choose when and where to call the library.
• When you use a framework, the framework is in charge of the flow.
• It provides you with a few places to plug in your code, but it calls the code you plugged in as needed.

Django Apps

• A Django Project is collection of multiple apps.
• These apps are standalone components.
• One app can be used in different projects and one project can have multiple apps.
• It promotes DRY (Do Not Repeat Yourself) principle.

Django MVT

• MVT stands for Model View Template.

• Django is based on MVT Pattern.

• It has four core components -

  • URLs -
    • Request sent by users' browsers come here.
    • Each URL is mapped with some view.
    • This mapping of URL and view is written is written in urls.py file.
  • Views -
    • A view is a python function written inside views.py file.
    • Each view is mapped/attached with a URL.
    • Whenever a request comes on a URL, view (function) mapped/attached to that URL is called.
    • A view interacts with tables (models) in database to fetch/store required data.
    • Finally, a view returns the response to user in form of templates.
  • Templates -
    • It is basically a HTML document which is returned as a response to the browser.
    • A view, fits in required data into the template (HTML file) and then returns the template.
    • HTML files are kept in a directory called templates in each app.
  • Models -

    • Models define the tables in the database with help of Object Oriented Programming.

    • These models are basically Python classes, which represent a Table in Database.

    • These classes are defined in models.py file.

    • Class Variables of Model (Class) represent Attributes/Columns of Table.

    • Instances/Objects of Model (Class) represent Rows/Tuple in Table.

    • Object Oriented Programming	Database
      Class	Table
      Class Variables	Columns
      Instances/Objects of Class	Rows/Tuple in table

• Generally, each app in a Django project has it's own urls, views, models, and templates.

• This promotes de-coupling and helps in making an app a standalone component.

A Real World Analogy

• Here, we will try to understand a real - world scenario.
• Later we will relate this real world scenario with Django to better understand components of Django.

Relating real-world analogy with Django

Setting up Django Project

• Step 1 - Install Python 3.

• Step 2 - Run python --version or python3 --version in your command prompt or terminal to check whether Python is successfully installed or not.

• Step 3 - Go to directory where you want to create the project.

• Step 4 - Make a new folder named Django_Projects.

• Step 5 - Right Click in that directory and open command prompt or terminal.

• Step 6 - Run the following command to create a virtual environment.

   python -m venv djenv
  

• Step 7 - Activate the environment.

  • In Windows run the following command -

   djenv\scripts\activate
  

  • In Linux/Mac run the following command -

   source djenv/bin/activate
  

  • After this step you should see environment name besides the command line as shown below.
  

• Step 8 - Download and install Django

   python -m pip install --upgrade pip
   pip install django
  

  • This will download and install necessary files.
  • To verify the installation type following command -

   python
   >>> import django
   >>> django.VERSION
  

  • If output matches with the following output, then django is properly installed. Your django version might be different from the one shown in this image.
  

• Step 9 - Starting a project in Django.

   django-admin startproject project1
  

  • project1 is just the project name.

• Step 10 - Open PyCharm Professional IDE. Open project1 in PyCharm.

• Step 11 - Setting Virtual environment for project in PyCharm

  • After opening project1 in PyCharm go to File and open Settings.
  • Click on Project:project1 and then select Project Interpreter.
  • Click on Settings icon, then click on Add and then select Existing Environment.
  • Select djenv/Scripts/python3.exe or djenv/bin/python3.exe from Interpreter dropdown and click OK.
  • Click OK again.
  • Now open the terminal in Pycharm and you'll see (djenv) written in it just like Step 7.

• Step 12 - Run following command in PyCharm's terminal

   python manage.py runserver
  

  • Then open the link from the terminal, if you see default Django Page with a rocket in it, then your installation was successful.

Some pre-existing files in Django Project

• settings.py file - It sets the basic configuration of the project like -
  • Language of Website,
  • Timezone to be used in website,
  • Database Engine of Website, etc
• manage.py file - It is used to perform various tasks related to project like -
  • Making a new app in project,
  • Starting the server,
  • Creating the database, etc.
  • We can write commands like python manage.py runserver.
• __init__.py file - It defines project1 as a Python package.
• wsgi.py file - It stands for Web Server Gateway Interface. It is used to forward requests from a web server (such as Apache or NGINX) to a backend Python web application or framework.

Content Contributors

• Ankit Sangwan
• Kshitiz Srivastava

Materials

• Django Video Tutorial Playlist (English)
• Django Video Tutorial Playlist (Hindi)
• Python Resources