Flask and Django

September 24, 2024 (1mo ago)

# Flask and Django Notes
 
## Flask
 
### Introduction to Flask
Flask is a micro web framework for Python. It is lightweight and modular, making it adaptable to developers’ needs.
 
### Key Features of Flask
- Lightweight and easy to use.
- Built-in development server and debugger.
- Integrated support for unit testing.
- RESTful request dispatching.
 
### Setting Up Flask
To get started with Flask, you need to install it first:
```bash
pip install Flask

Basic Flask Application

Here’s a simple example of a Flask application:

from flask import Flask
 
app = Flask(__name__)
 
@app.route('/')
def home():
    return "Hello, Flask!"
 
if __name__ == '__main__':
    app.run(debug=True)

Routing

Flask uses decorators to define routes.

@app.route('/about')
def about():
    return "About Page"

Request and Response

You can handle HTTP requests and responses using Flask’s built-in objects.

from flask import request
 
@app.route('/greet', methods=['POST'])
def greet():
    name = request.form.get('name')
    return f"Hello, {name}!"

Template Rendering

Flask uses Jinja2 as its template engine. Here’s how to render a template:

from flask import render_template
 
@app.route('/hello/<name>')
def hello(name):
    return render_template('hello.html', name=name)

Handling Forms

You can handle forms easily in Flask.

from flask import request, redirect, url_for
 
@app.route('/submit', methods=['POST'])
def submit():
    data = request.form['data']
    # Process the data
    return redirect(url_for('home'))

Flask Extensions

Flask has many extensions that add functionality to the core framework. Some popular extensions include:

Django

Introduction to Django

Django is a high-level Python web framework that encourages rapid development and clean, pragmatic design.

Key Features of Django

Setting Up Django

To start a new Django project, you need to install Django:

pip install Django

Creating a Django Project

Create a new project using the Django command-line tool.

django-admin startproject myproject
cd myproject
python manage.py runserver

Creating a Django App

Django projects are made up of applications. Create a new app with:

python manage.py startapp myapp

URL Routing in Django

Define URLs in your app’s urls.py file.

from django.urls import path
from . import views
 
urlpatterns = [
    path('', views.home, name='home'),
]

Views in Django

Views are functions that handle the logic of your application.

from django.http import HttpResponse
 
def home(request):
    return HttpResponse("Hello, Django!")

Template Rendering

Django uses a templating engine to render HTML pages.

<!-- templates/home.html -->
<h1>Hello, {{ name }}!</h1>
from django.shortcuts import render
 
def home(request):
    return render(request, 'home.html', {'name': 'Django'})

Handling Forms

Django provides form handling utilities.

from django import forms
 
class MyForm(forms.Form):
    name = forms.CharField(label='Your name', max_length=100)

Model Definition

Django’s ORM allows you to define models to interact with the database.

from django.db import models
 
class Post(models.Model):
    title = models.CharField(max_length=100)
    content = models.TextField()
    created_at = models.DateTimeField(auto_now_add=True)

Django Admin Interface

Django automatically creates an admin interface for your models. To use it, register your models in admin.py.

from django.contrib import admin
from .models import Post
 
admin.site.register(Post)

Flask and Django Interview Questions

Flask Interview Questions

  1. What is Flask? Flask is a micro web framework for Python that provides a simple way to build web applications.

  2. What are Flask decorators? Decorators in Flask are used to wrap functions with additional functionality, commonly used for routing.

  3. How does Flask handle sessions? Flask uses a secure cookie to store session data on the client-side.

  4. What are Flask extensions? Flask extensions are packages that add functionality to the core Flask framework, such as database integration and form handling.

  5. What is Jinja2? Jinja2 is the templating engine used by Flask for rendering HTML pages.

Django Interview Questions

  1. What is Django? Django is a high-level web framework for Python that promotes rapid development and clean, pragmatic design.

  2. What is the purpose of Django’s ORM? Django’s ORM allows developers to interact with the database using Python objects instead of SQL queries.

  3. How do you create a new Django project? You can create a new Django project using the command django-admin startproject projectname.

  4. What are middleware in Django? Middleware are hooks into Django's request/response processing. They're used to process requests globally before reaching the view or after the view has processed them.

  5. What is the Django admin interface? The Django admin interface is an automatically generated web-based interface that allows you to manage your application’s data.

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