In the previous lesson, we learned about GUI Programming using Tkinter and how Python can be used to create desktop applications. Today, we will learn about Web Development with Flask, one of the most popular Python web frameworks.
Flask helps developers create:
- Websites
- Web applications
- APIs
- Dashboards
- Online systems
Flask is lightweight, simple, and beginner-friendly.
What is Flask?
Flask is a Python web framework used to build web applications.
A Framework is a collection of tools and libraries that simplify application development.
Flask helps developers:
- Handle web requests
- Create web pages
- Manage routes
- Process forms
- Build APIs
Why Flask is Important
Flask helps programmers:
- Build web applications quickly
- Create REST APIs
- Develop scalable systems
- Simplify backend development
- Build dynamic websites
Many developers prefer Flask because of its simplicity and flexibility.
Installing Flask
Flask is installed using "pip".
Example
pip install flask
Importing Flask
Example
from flask import Flask
Creating a Flask Application
Example
from flask import Flask
app = Flask(name)
This creates a Flask application object.
Running a Flask Server
Example
from flask import Flask
app = Flask(name)
@app.route("/")
def home():
return "Welcome to Flask"
app.run()
Understanding Routes
Routes define URLs in a web application.
Example
@app.route("/")
def home():
return "Home Page"
When users visit "/", Flask displays ""Home Page"".
Multiple Routes
Example
from flask import Flask
app = Flask(name)
@app.route("/")
def home():
return "Home Page"
@app.route("/about")
def about():
return "About Page"
app.run()
Debug Mode in Flask
Debug mode automatically reloads the server after code changes.
Example
app.run(debug=True)
Returning HTML Content
Flask can return HTML code.
Example
@app.route("/")
def home():
return "
Welcome to Flask
"Using Templates in Flask
Templates help separate HTML from Python code.
Flask uses the "templates" folder for HTML files.
Example Structure
project/
app.py
templates/
index.html
Rendering HTML Templates
Example
from flask import Flask, render_template
app = Flask(name)
@app.route("/")
def home():
return render_template("index.html")
app.run()
Handling User Input with Forms
Flask can process form data submitted by users.
Example
from flask import Flask, request
app = Flask(name)
@app.route("/login", methods=["POST"])
def login():
username = request.form["username"]
return "Welcome " + username
Using GET and POST Methods
Method| Purpose
"GET"| Retrieve data
"POST"| Submit data
Flask Static Files
Static files include:
- CSS
- JavaScript
- Images
Flask stores them inside a "static" folder.
Example Structure
project/
static/
style.css
Flask URL Parameters
Flask can receive values from URLs.
Example
@app.route("/user/")
def user(name):
return "Hello " + name
If the user visits:
/user/Augustine
Output:
Hello Augustine
Connecting Flask with Databases
Flask applications can connect with databases such as:
- SQLite
- MySQL
- PostgreSQL
Example
import sqlite3
Simple Flask Application Example
Example
from flask import Flask
app = Flask(name)
@app.route("/")
def home():
return "Welcome to Python Flask"
@app.route("/about")
def about():
return "This is the About Page"
app.run(debug=True)
Advantages of Flask
Flask helps developers:
- Build web applications quickly
- Create APIs easily
- Write clean code
- Scale applications
- Manage backend systems efficiently
Flask is widely used in modern web development.
Real-World Applications of Flask
Flask is used in:
- Blogging Systems
- Portfolio Websites
- REST APIs
- School Management Systems
- E-Commerce Platforms
- Admin Dashboards
Conclusion
Flask is a powerful and beginner-friendly Python framework for web development. It helps developers create websites, APIs, and backend systems efficiently.
Understanding Flask is important for anyone interested in Python web development and backend programming.
Practice creating routes, templates, and simple web applications to strengthen your Flask development skills.
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