2. Introduction to Flask:
Flask is a micro-framework for Python.
It is lightweight and easy to use, ideal for small to medium web applications.
Flask is often used for developing RESTful APIs, websites, and web services.
4. Creating a Simple Flask Application:
from flask import Flask
app = Flask(__name__)
@app.route('/')
def hello_world():
return "Hello, World!"
if __name__ == '__main__':
app.run(debug=True)
•app = Flask(__name__) initializes the app.
•@app.route('/') creates a route for the
homepage.
•app.run(debug=True) runs the app with the
debug mode on.
5. Routing in Flask:
•Routes are used to map URLs to functions.
•Example of a dynamic route:
@app.route('/user/<username>’)
def show_user(username):
return f'Hello, {username}!'
6. Template Rendering with Jinja:
Flask uses Jinja templating engine.
Templates allow dynamic HTML generation.
<!-- Example: hello.html -->
<h1>Hello, {{ name }}!</h1>
In Flask:
from flask import render_template
@app.route('/greet/<name>’)
def greet(name):
return render_template('hello.html', name=name)
7. Flask and Database Integration:
•Flask supports several databases via extensions like:
•Flask-MySql connector (SQL databases)
•Flask-MongoEngine (NoSQL, MongoDB)
•Example with MySql Connector:
import mysql.connector
from flask import Flask
app = Flask(__name__)
def get_db_connection():
connection = mysql.connector.connect(
host='localhost',
user='your_username',
password='your_password',
database='your_database'
)
return connection
8. Create a Table:
@app.route('/create_table')
def create_table():
connection = get_db_connection()
cursor = connection.cursor()
# Create a new table
cursor.execute("""CREATE TABLE IF NOT EXISTS users (id INT AUTO_INCREMENT PRIMARY KEY,name VARCHAR(100),email VARCHAR(100) ) """)
connection.commit()
cursor.close()
connection.close()
return "Table created successfully!"
9. Insert Data:
@app.route('/insert')
def insert_data():
connection = get_db_connection()
cursor = connection.cursor()
# Insert data into the table
cursor.execute("""
INSERT INTO users (name, email)
VALUES (%s, %s)
""", ('John Doe', 'john@example.com'))
connection.commit()
cursor.close()
connection.close()
return "Data inserted successfully!"
10. Read Data:
@app.route('/fetch')
def fetch_data():
connection = get_db_connection()
cursor = connection.cursor()
# Fetch all rows from the table
cursor.execute("SELECT * FROM users")
rows = cursor.fetchall()
cursor.close()
connection.close()
return str(rows)
11. Update Data:
@app.route('/update')
def update_data():
connection = get_db_connection()
cursor = connection.cursor()
# Update user data
cursor.execute("""UPDATE users SET email = %s WHERE name = %s
""", ('newemail@example.com', 'John Doe'))
connection.commit()
cursor.close()
connection.close()
return "Data updated successfully!"
12. Delete Data:
@app.route('/delete')
def delete_data():
connection = get_db_connection()
cursor = connection.cursor()
# Delete a record
cursor.execute("DELETE FROM users WHERE name = %s", ('John Doe',))
connection.commit()
cursor.close()
connection.close()
return "Data deleted successfully!"
