1. Install Flask

pip install flask

2. Create a New Flask App

from flask import Flask
app = Flask(__name__)

3. Run the Flask App

if __name__ == '__main__':
    app.run()

4. Define a Route

@app.route('/')
def home():
    return 'Hello, World!'

5. Use a Template

from flask import render_template

@app.route('/')
def home():
    return render_template('home.html')

6. Handle Form Data

from flask import request

@app.route('/submit', methods=['POST'])
def submit():
    name = request.form['name']
    return 'Hello, ' + name + '!'

7. Use a Database

from flask_sqlalchemy import SQLAlchemy

app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///mydatabase.db'
db = SQLAlchemy(app)

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(100), nullable=False)

@app.route('/users')
def users():
    users = User.query.all()
    return render_template('users.html', users=users)

8. Use Flask-WTF for Forms

from flask_wtf import FlaskForm
from wtforms import StringField, SubmitField

class MyForm(FlaskForm):
    name = StringField('Name')
    submit = SubmitField('Submit')

@app.route('/myform', methods=['GET', 'POST'])
def myform():
    form = MyForm()
    if form.validate_on_submit():
        return 'Hello, ' + form.name.data + '!'
    return render_template('myform.html', form=form)

9. Use Flask-Login for Authentication

from flask_login import LoginManager, UserMixin, login_user, logout_user

app.config['SECRET_KEY'] = 'secret_key'

login_manager = LoginManager(app)

class User(UserMixin):
    def __init__(self, id):
        self.id = id

@login_manager.user_loader
def load_user(user_id):
    return User(user_id)

@app.route('/login', methods=['GET', 'POST'])
def login():
    if request.method == 'POST':
        username = request.form['username']
        password = request.form['password']
        user = User(username)
        login_user(user)
        return 'Logged in!'
    return render_template('login.html')

10. Use Flask-Mail for Email

from flask_mail import Mail, Message

app.config['MAIL_SERVER'] = 'smtp.gmail.com'
app.config['MAIL_PORT'] = 465
app.config['MAIL_USE_TLS'] = False
app.config['MAIL_USE_SSL'] = True
app.config['MAIL_USERNAME'] = 'your_email@gmail.com'
app.config['MAIL_PASSWORD'] = 'your_password'

mail = Mail(app)

@app.route('/send_email')
def send_email():
    msg = Message('Hello', sender='your_email@gmail.com', recipients=['recipient_email@gmail.com'])
    msg.body = 'This is a test email'
    mail.send(msg)
    return 'Email sent!'

11. Use Flask-RESTful for APIs

from flask_restful import Api, Resource

api = Api(app)

class HelloWorld(Resource):
    def get(self):
        return {'hello': 'world'}

api.add_resource(HelloWorld, '/')

12. Use Flask-Cors for CORS

from flask_cors import CORS

cors = CORS(app, resources={r"/api/*": {"origins": "*"}})

13. Use Flask-DebugToolbar for Debugging

from flask_debugtoolbar import DebugToolbarExtension

app.config['DEBUG_TB_ENABLED'] = True
toolbar = DebugToolbarExtension(app)

14. Use Flask-Profiler for Profiling

from flask_profiler import Profiler

profiler = Profiler(app)

15. Use Flask-Testing for Testing

from flask_testing import TestCase

class MyTest(TestCase):
    def create_app(self):
        app.config['TESTING'] = True
        return app

    def test_home(self):
        response = self.client.get('/')
        self.assertEqual(response.data, b'Hello, World!')

16. Use Flask-SocketIO for WebSockets

from flask_socketio import SocketIO

socketio = SocketIO(app)

@socketio.on('message')
def handle_message(msg):
    print('Message: ' + msg)

17. Use Flask-Session for Server-Side Sessions

from flask_session import Session

app.config['SESSION_TYPE'] = 'filesystem'
Session(app)

18. Use Flask-Admin for Admin Interface

from flask_admin import Admin

admin = Admin(app)
admin.add_view(ModelView(User, db.session))

19. Use Flask-Migrate for Database Migrations

from flask_migrate import Migrate

migrate = Migrate(app, db)

20. Use Flask-Cache for Caching

from flask_caching import Cache

cache = Cache(app)

21. Use Flask-Babel for Internationalization

from flask_babel import Babel

babel = Babel(app)

22. Use Flask-RESTPlus for REST APIs

from flask_restplus import Api

api = Api(app)

23. Use Flask-Uploads for File Uploads

from flask_uploads import UploadSet, configure_uploads

photos = UploadSet('photos', ('jpg', 'png'))
configure_uploads(app, photos)

24. Use Flask-Admin for CRUD Operations

from flask_admin.contrib.sqla import ModelView

admin.add_view(ModelView(User, db.session))

25. Use Flask-RESTful for Resource-Based APIs

class UserResource(Resource):
    def get(self, user_id):
        user = User.query.get(user_id)
        return {'name': user.name}

api.add_resource(UserResource, '/user/<int:user_id>')

26. Use Flask-Login for User Sessions

@app.route('/logout')
def logout():
    logout_user()
    return 'Logged out!'

27. Use Flask-WTF for CSRF Protection

@app.route('/form', methods=['GET', 'POST'])
def form():
    form = MyForm()
    if form.validate_on_submit():
        return 'Form submitted!'
    return render_template('form.html', form=form)

28. Use Flask-SQLAlchemy for ORM

db.create_all()

29. Use Flask-RESTful for Error Handling

@app.errorhandler(404)
def not_found(error):
    return {'message': 'Not found'}, 404

30. Use Flask-RESTful for Input Validation

from flask_restful import reqparse

parser = reqparse.RequestParser()
parser.add_argument('name', type=str, required=True)
args = parser.parse_args()

31. Use Flask-RESTful for Pagination

@app.route('/users')
def get_users():
    page = request.args.get('page', 1, type=int)
    users = User.query.paginate(page, per_page=10)
    return {'users': [user.name for user in users.items]}

32. Use Flask-RESTful for Filtering

@app.route('/users')
def get_filtered_users():
    name = request.args.get('name')
    users = User.query.filter(User.name.contains(name)).all()
    return {'users': [user.name for user in users]}

33. Use Flask-RESTful for Sorting

@app.route('/users')
def get_sorted_users():
    users = User.query.order_by(User.name).all()
    return {'users': [user.name for user in users]}

34. Use Flask-RESTful for Batch Processing

@app.route('/users', methods=['POST'])
def create_users():
    data = request.get_json()
    for user_data in data['users']:
        user = User(name=user_data['name'])
        db.session.add(user)
    db.session.commit()
    return {'message': 'Users created!'}

35. Use Flask-RESTful for Rate Limiting

from flask_limiter import Limiter

limiter = Limiter(app, key_func=get_remote_address)

@app.route('/limited')
@limiter.limit("5 per minute")
def limited():
    return 'This route is rate limited!'

36. Use Flask-RESTful for Caching

@app.route('/cached')
@cache.cached(timeout=60)
def cached():
    return 'This response is cached for 60 seconds!'

37. Use Flask-RESTful for API Versioning

api_v1 = Api(app, version='1.0', title='API V1')
api_v2 = Api(app, version='2.0', title='API V2')

38. Use Flask-RESTful for Custom Error Messages

@app.errorhandler(400)
def bad_request(error):
    return {'message': 'Bad request'}, 400

39. Use Flask-RESTful for Custom Response Formats

@app.route('/json')
def json_response():
    return jsonify({'message': 'This is a JSON response!'})

40. Use Flask-RESTful for XML Responses

@app.route('/xml')
def xml_response():
    return Response('<message>This is an XML response!</message>', mimetype='application/xml')

41. Use Flask-RESTful for File Downloads

@app.route('/download')
def download_file():
    return send_file('path/to/file.txt', as_attachment=True)

42. Use Flask-RESTful for File Uploads

@app.route('/upload', methods=['POST'])
def upload_file():
    file = request.files['file']
    file.save('uploads/' + file.filename)
    return 'File uploaded!'

43. Use Flask-RESTful for Background Tasks

from flask import jsonify
from threading import Thread

def background_task():
    # Perform some background task
    pass

@app.route('/start_task')
def start_task():
    thread = Thread(target=background_task)
    thread.start()
    return jsonify({'message': 'Task started!'})

44. Use Flask-RESTful for WebSocket Communication

@socketio.on('connect')
def handle_connect():
    print('Client connected!')

@socketio.on('disconnect')
def handle_disconnect():
    print('Client disconnected!')

45. Use Flask-RESTful for JWT Authentication

from flask_jwt_extended import JWTManager, create_access_token

app.config['JWT_SECRET_KEY'] = 'your_jwt_secret_key'
jwt = JWTManager(app)

@app.route('/login', methods=['POST'])
def login():
    username = request.json['username']
    access_token = create_access_token(identity=username)
    return jsonify(access_token=access_token)

46. Use Flask-RESTful for OAuth2 Authentication

from flask_oauthlib.provider import OAuth2Provider

oauth = OAuth2Provider(app)

47. Use Flask-RESTful for API Documentation

from flask_restplus import Api

api = Api(app, doc='/docs')

48. Use Flask-RESTful for API Testing

from flask_testing import TestCase

class MyTest(TestCase):
    def create_app(self):
        app.config['TESTING'] = True
        return app

    def test_api(self):
        response = self.client.get('/api/resource')
        self.assertEqual(response.status_code, 200)

49. Use Flask-RESTful for API Rate Limiting

from flask_limiter import Limiter

limiter = Limiter(app)

@app.route('/rate_limited')
@limiter.limit("10 per hour")
def rate_limited():
    return 'This route is rate limited!'

50. Use Flask-RESTful for API Versioning

api_v1 = Api(app, version='1.0', title='API V1')
api_v2 = Api(app, version='2.0', title='API V2')

51. Use Flask-RESTful for API Pagination

@app.route('/items')
def get_items():
    page = request.args.get('page',  1, type=int)
    items = Item.query.paginate(page, per_page=10)
    return {'items': [item.name for item in items.items]}

52. Use Flask-RESTful for API Filtering

@app.route('/items')
def get_filtered_items():
    name = request.args.get('name')
    items = Item.query.filter(Item.name.contains(name)).all()
    return {'items': [item.name for item in items]}

53. Use Flask-RESTful for API Sorting

@app.route('/items')
def get_sorted_items():
    items = Item.query.order_by(Item.name).all()
    return {'items': [item.name for item in items]}

54. Use Flask-RESTful for API Batch Processing

@app.route('/items', methods=['POST'])
def create_items():
    data = request.get_json()
    for item_data in data['items']:
        item = Item(name=item_data['name'])
        db.session.add(item)
    db.session.commit()
    return {'message': 'Items created!'}

55. Use Flask-RESTful for API Error Handling

@app.errorhandler(404)
def not_found(error):
    return {'message': 'Not found'}, 404

56. Use Flask-RESTful for API Input Validation

from flask_restful import reqparse

parser = reqparse.RequestParser()
parser.add_argument('name', type=str, required=True)
args = parser.parse_args()

57. Use Flask-RESTful for API Response Formatting

@app.route('/json')
def json_response():
    return jsonify({'message': 'This is a JSON response!'})

58. Use Flask-RESTful for XML Responses

@app.route('/xml')
def xml_response():
    return Response('<message>This is an XML response!</message>', mimetype='application/xml')

59. Use Flask-RESTful for File Downloads

@app.route('/download')
def download_file():
    return send_file('path/to/file.txt', as_attachment=True)

60. Use Flask-RESTful for File Uploads

@app.route('/upload', methods=['POST'])
def upload_file():
    file = request.files['file']
    file.save('uploads/' + file.filename)
    return 'File uploaded!'

61. Use Flask-RESTful for Background Tasks

from threading import Thread

def background_task():
    # Perform some background task
    pass

@app.route('/start_task')
def start_task():
    thread = Thread(target=background_task)
    thread.start()
    return jsonify({'message': 'Task started!'})

62. Use Flask-RESTful for WebSocket Communication

@socketio.on('connect')
def handle_connect():
    print('Client connected!')

@socketio.on('disconnect')
def handle_disconnect():
    print('Client disconnected!')

63. Use Flask-RESTful for JWT Authentication

from flask_jwt_extended import JWTManager, create_access_token

app.config['JWT_SECRET_KEY'] = 'your_jwt_secret_key'
jwt = JWTManager(app)

@app.route('/login', methods=['POST'])
def login():
    username = request.json['username']
    access_token = create_access_token(identity=username)
    return jsonify(access_token=access_token)

64. Use Flask-RESTful for OAuth2 Authentication

from flask_oauthlib.provider import OAuth2Provider

oauth = OAuth2Provider(app)

65. Use Flask-RESTful for API Documentation

from flask_restplus import Api

api = Api(app, doc='/docs')

66. Use Flask-RESTful for API Testing

from flask_testing import TestCase

class MyTest(TestCase):
    def create_app(self):
        app.config['TESTING'] = True
        return app

    def test_api(self):
        response = self.client.get('/api/resource')
        self.assertEqual(response.status_code, 200)

67. Use Flask-RESTful for API Rate Limiting

from flask_limiter import Limiter

limiter = Limiter(app)

@app.route('/rate_limited')
@limiter.limit("10 per hour")
def rate_limited():
    return 'This route is rate limited!'

68. Use Flask-RESTful for API Versioning

api_v1 = Api(app, version='1.0', title='API V1')
api_v2 = Api(app, version='2.0', title='API V2')

69. Use Flask-RESTful for API Pagination

@app.route('/items')
def get_items():
    page = request.args.get('page', 1, type=int)
    items = Item.query.paginate(page, per_page=10)
    return {'items': [item.name for item in items.items]}

70. Use Flask-RESTful for API Filtering

@app.route('/items')
def get_filtered_items():
    name = request.args.get('name')
    items = Item.query.filter(Item.name.contains(name)).all()
    return {'items': [item.name for item in items]}

71. Use Flask-RESTful for API Sorting

@app.route('/items')
def get_sorted_items():
    items = Item.query.order_by(Item.name).all()
    return {'items': [item.name for item in items]}

72. Use Flask-RESTful for API Batch Processing

@app.route('/items', methods=['POST'])
def create_items():
    data = request.get_json()
    for item_data in data['items']:
        item = Item(name=item_data['name'])
        db.session.add(item)
    db.session.commit()
    return {'message': 'Items created!'}

73. Use Flask-RESTful for API Error Handling

@app.errorhandler(404)
def not_found(error):
    return {'message': 'Not found'}, 404

74. Use Flask-RESTful for API Input Validation

from flask_restful import reqparse

parser = reqparse.RequestParser()
parser.add_argument('name', type=str, required=True)
args = parser.parse_args()

75. Use Flask-RESTful for API Response Formatting

@app.route('/json')
def json_response():
    return jsonify({'message': 'This is a JSON response!'})

76. Use Flask-RESTful for XML Responses

@app.route('/xml')
def xml_response():
    return Response('<message>This is an XML response!</message>', mimetype='application/xml')

77. Use Flask-RESTful for File Downloads

@app.route('/download')
def download_file():
    return send_file('path/to/file.txt', as_attachment=True)

78. Use Flask-RESTful for File Uploads

@app.route('/upload', methods=['POST'])
def upload_file():
    file = request.files['file']
    file.save('uploads/' + file.filename)
    return 'File uploaded!'

79. Use Flask-RESTful for Background Tasks

from threading import Thread

def background_task():
    # Perform some background task
    pass

@app.route('/start_task')
def start_task():
    thread = Thread(target=background_task)
    thread.start()
    return jsonify({'message': 'Task started!'})

80. Use Flask-RESTful for WebSocket Communication

@socketio.on('connect')
def handle_connect():
    print('Client connected!')

@socketio.on('disconnect')
def handle_disconnect():
    print('Client disconnected!')

81. Use Flask-RESTful for JWT Authentication

from flask_jwt_extended import JWTManager, create_access_token

app.config['JWT_SECRET_KEY'] = 'your_jwt_secret_key'
jwt = JWTManager(app)

@app.route('/login', methods=['POST'])
def login():
    username = request.json['username']
    access_token = create_access_token(identity=username)
    return jsonify(access_token=access_token)

82. Use Flask-RESTful for OAuth2 Authentication

from flask_oauthlib.provider import OAuth2Provider

oauth = OAuth2Provider(app)

83. Use Flask-RESTful for API Documentation

from flask_restplus import Api

api = Api(app, doc='/docs')

84. Use Flask-RESTful for API Testing

from flask_testing import TestCase

class MyTest(TestCase):
    def create_app(self):
        app.config['TESTING'] = True
        return app

    def test_api(self):
        response = self.client.get('/api/resource')
        self.assertEqual(response.status_code, 200)

85. Use Flask-RESTful for API Rate Limiting

from flask_limiter import Limiter

limiter = Limiter(app)

@app.route('/rate_limited')
@limiter.limit("10 per hour")
def rate_limited():
    return 'This route is rate limited!'

86. Use Flask-RESTful for API Versioning

api_v1 = Api(app, version='1.0', title='API V1')
api_v2 = Api(app, version='2.0', title='API V2')

87. Use Flask-RESTful for API Pagination

@app.route('/items')
def get_items():
    page = request.args.get('page', 1, type=int)
    items = Item.query.paginate(page, per_page=10)
    return {'items': [item.name for item in items.items]}

88. Use Flask-RESTful for API Filtering

@app.route('/items')
def get_filtered_items():
    name = request.args.get('name')
    items = Item.query.filter(Item.name.contains(name)).all()
    return {'items': [item.name for item in items]}

89. Use Flask-RESTful for API Sorting

@app.route('/items')
def get_sorted_items():
    items = Item.query.order_by(Item.name).all()
    return {'items': [item.name for item in items]}

90. Use Flask-RESTful for API Batch Processing

@app.route('/items', methods=['POST'])
def create_items():
    data = request.get_json()
    for item_data in data['items']:
        item = Item(name=item_data['name'])
        db.session.add(item)
    db.session.commit()
    return {'message': 'Items created!'}

91. Use Flask-RESTful for API Error Handling

@app.errorhandler(404)
def not_found(error):
    return {'message': 'Not found'}, 404

92. Use Flask-RESTful for API Input Validation

from flask_restful import reqparse

parser = reqparse.RequestParser()
parser.add_argument('name', type=str, required=True)
args = parser.parse_args()

93. Use Flask-RESTful for API Response Formatting

@app.route('/json')
def json_response():
    return jsonify({'message': 'This is a JSON response!'})

94. Use Flask-RESTful for XML Responses

@app.route('/xml')
def xml_response():
    return Response('<message>This is an XML response!</message>', mimetype='application/xml')

95. Use Flask-RESTful for File Downloads

@app.route('/download')
def download_file():
    return send_file('path/to/file.txt', as_attachment=True)

96. Use Flask-RESTful for File Uploads

@app.route('/upload', methods=['POST'])
def upload_file():
    file = request.files['file']
    file.save('uploads/' + file.filename)
    return 'File uploaded!'

97. Use Flask-RESTful for Background Tasks

from threading import Thread

def background_task():
    # Perform some background task
    pass

@app.route('/start_task')
def start_task():
    thread = Thread(target=background_task)
    thread.start()
    return jsonify({'message': 'Task started!'})

98. Use Flask-RESTful for WebSocket Communication

@socketio.on('connect')
def handle_connect():
    print('Client connected!')

@socketio.on('disconnect')
def handle_disconnect():
    print('Client disconnected!')

99. Use Flask-RESTful for JWT Authentication

from flask_jwt_extended import JWTManager, create_access_token

app.config['JWT_SECRET_KEY'] = 'your_jwt_secret_key'
jwt = JWTManager(app)

@app.route('/login', methods=['POST'])
def login():
    username = request.json['username']
    access_token = create_access_token(identity=username)
    return jsonify(access_token=access_token)

100. Use Flask-RESTful for OAuth2 Authentication

from flask_oauthlib.provider import OAuth2Provider

oauth = OAuth2Provider(app)