Python Flask Web Development Tutorial in Hindi

Open the Project Directory

|project

Install Virtual Virtual Environment

pip install virtualenv 

Create Virtual Environment

virtualenv env

project
└── env

Note:- In a system you can install only one version of Software, let python. If you want to install different versions and packages for it, without disturbing the Orginal python. you can create a virtual environment

If you see error to execute the script in powershell, change execution policy.

Set-ExecutionPolicy unrestricted

Activate Virtual Environment every time you open a new terminal

# activate in powershell -> ps1
.\env\Scripts\activate.ps1

trick:- type env and hit tab it will autocomplete to .\env\Scripts\

Install flask

pip install flask

note:- Installing modules in global interpreter will not able to run in this environment apps. so be carefull to install them. the will automatically install in your /env directory of your project

Flask Minimal App

# app
from flask import Flask
app = Flask(_name_)
 
@app.route('/')
def hello_world():
    return 'Hello, World!'

# Call or run the app.
if __name__ == "__main__":
    app.run(debug=True)

Save it as app.py

project
├── env
└── app.py

This code block does the following:

• if __name__ == "__main__": checks if the script is being run directly (not imported as a module).
• app.run(debug=True) starts the Flask web server with debug mode enabled

trick: in vs code to open terminal using "Ctrl + Shift+ `"

Run the program

py ./app.py
#or
python ./app.py

Output

Running on http://127.0.0.1:5000

open the link and hurray!, your app is working.

to change the server from 5000 to 8000

# Change the line
if __name__ == "__main__":
    app.run(debug=True, port=8000)

note: - on save, flask will automatically reload the devlopment server like nodemone

Add another routes

@app.route('/products')
def products():
    return 'This is products page'

save it and see the output at http://127.0.0.1:8000/products

Like this, we can Create multiple endpoints in our website.

Static and Template

project
├── env
├── static
│     └── gaurav.txt 
├── template
│      └── index.html
└── app.py

Static Directory: - any file in the static directory can be accessed using http://127.0.0.1:8000/static/gaurav.txt So never store important file, which you don't want to show to public.

Template Directoy : It is use to store files like .html to render to your route. let render index.htm to route ('./')

Change these snippets

# add render_templat e
from flask import Flask, render_template

# return render(template('index.html)')
@app.route('/')
def hellow_world():
    return render_template('index.html')

Consider that your index.html have frontend part, a "To Do Manager"

Database in Flask

To use database in Flask , we have to use SQL Alchemy

SQL alchemy is a "ORM Mapper", that provide facilities to change in database through python

flask Alchemy documentation

install SQL alchemy

pip install flask-sqlalchemy

import sql alchemy

from flask_sqlalchemy import SQLAlchemy

# Update the app
app = Flask(__name__)
# configuration key
app.config['SQLALCHEMY_DATABASE_uri'] = "sqlite:///todo.db"
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = "sqlite:///todo.db"
db = SQLAlchemy(app)
 
# Make a todo Class
class Todo(db.Model):
    sno = db.Column(db.Integer, primary_key=True)
    title = db.Column(db.String(200), nullable=False)
    desc = db.Column(db.String(200), nullable=False)
    date_created = db.Column(db.DateTime,(200), nullable = False)
 
    # function
    def __rpr__(self) -> str: #  the -> str part is known as a type hint or type annotation. It indicates the return type of the function
        return f"{self.sno} - {self.title}"

note:- make sure to import datetime for this class.

Use python interpreter terminal, To create the database:

import app import db

db.create_all()

exit()

project
├── __pycache__
├── env
├── static
│     └── gaurav.txt 
├── template
│      └── index.html
├── app.py
└── todo.db

Drag and drop the todo.db file to Online SQLite Viewer to see your database

Create a Todo Instances for HomePage

@app.route('/')
def hello_world():
    # this will input data in database
    todo = Todo(title="First Todo", desc="Start investing in Stock market")
    db.session.add(todo)
    db.session.commit()
    return render_template('index.html')

Create a Route to show data in Database

@app.route('/show')
def products():
    allTodo = Todo.query.all()
    print(allTodo)
    return 'this is products page'

Output will be display at terminal, whenever you visit http://127.0.0.1:8000/shows

53:00 / 1:47:13 ⚠️

Also notes of Jinja Template engine