Flask Tutorial

Learn what Flask is, why it is called a microframework, and what kinds of Python web apps it can build.

Compare Flask and Django so you can choose the right Python web framework for different beginner projects.

Set up a Flask 3.x project with a virtual environment, install Flask, and confirm the command line tools work.

Create a first Flask app with routes, simple responses, and the modern `flask --app` command.

Use the Flask development server safely, understand debug mode, and work with the automatic reloader.

Learn how Flask routes map URLs to view functions and how to organize simple page handlers.

Use dynamic URL segments and converters to capture values from paths in Flask routes.

Understand HTTP methods and configure Flask routes that respond to GET, POST, and other request types.

Generate URLs with `url_for()` instead of hardcoding paths in Flask views and templates.

Read query strings, form data, headers, and JSON input from Flask requests.

Return strings, HTML, JSON, tuples, response objects, and meaningful status codes from Flask views.

Send users to another URL with redirects and stop requests with `abort()` for standard error responses.

Render HTML templates with Flask and pass Python data into Jinja2 pages.

Create a shared base template with Jinja blocks so pages can reuse layout, navigation, and structure.

Use Jinja filters, if statements, loops, and empty states to make templates more expressive.

Serve CSS, JavaScript, and images from Flask's `static/` folder and link to them with `url_for()`.

Build plain HTML forms, submit them to Flask routes, validate simple input, and redirect after POST.

Use Flask-WTF and WTForms for structured form classes, validation, CSRF protection, and cleaner templates.

Show one-time success, error, and info messages after redirects with Flask's flashing system.

Store small pieces of user-specific state with Flask sessions, such as display names or simple preferences.

Read, set, and delete browser cookies in Flask while understanding how cookies differ from sessions.

Create friendly custom pages for common Flask errors such as 404 Not Found and 500 Server Error.

Manage Flask configuration values for secrets, debug settings, feature flags, and environment-specific behavior.

Structure Flask apps with a `create_app()` function so configuration, tests, extensions, and blueprints are easier to manage.

Organize related routes with Flask blueprints and register them in an application factory.

Install Flask-SQLAlchemy, configure a database URL, and initialize the extension with the application factory pattern.

Define SQLAlchemy models with columns, constraints, defaults, and helpful representation methods.

Use Flask-Migrate to create, review, and apply Alembic migrations as your database schema changes.

Build create, read, update, and delete routes using SQLAlchemy sessions and Flask redirects.

Connect models with one-to-many and many-to-many relationships using foreign keys and relationship attributes.

Write focused SQLAlchemy queries with filters, ordering, joins, pagination, eager loading, and aggregate counts.

Store passwords safely with Werkzeug hashing helpers and never keep raw passwords in the database.

Add session-based user authentication with Flask-Login, user loaders, login_user, logout_user, and current_user.

Put practical authentication routes, templates, validation, flash messages, and redirects together.

Restrict pages to logged-in users and add role-based authorization decorators for admin-only behavior.

Accept uploaded files safely, validate filenames and extensions, store files, and serve uploaded assets.

Configure Flask-Mailman style SMTP settings, send transactional email, and keep email sending testable.

Split long result sets into pages using Flask-SQLAlchemy paginate() and build page navigation links.

Build search and filter routes that compose SQLAlchemy conditions from query string parameters.

Design resource-oriented Flask routes with HTTP methods, status codes, and JSON responses.

Create consistent JSON serialization, request validation, and response envelopes for Flask APIs.

Return useful JSON errors with custom error handlers, abort descriptions, validation errors, and database rollback.

Configure Cross-Origin Resource Sharing so browser frontends can call your Flask API safely.

Add flask commands for database seeding, user creation, maintenance tasks, and local automation.

Use Python logging in Flask apps to record errors, request context, and operational events.

Write pytest tests for Flask routes, app factories, database behavior, and authenticated clients.

Use Flask request hooks and context processors to prepare request data and share template helpers.

Choose common Flask extensions for forms, auth, databases, APIs, admin panels, caching, and background jobs.

Protect a Flask application with safe configuration, password hashing, session settings, authorization checks, and production habits.

Defend Flask forms and templates against CSRF, XSS, clickjacking, MIME sniffing, and common browser-side security mistakes.

Organize a larger Flask codebase with an application factory, extensions module, feature packages, service functions, and clear boundaries.

Use Flask blueprints for large features, nested URL design, error handlers, template organization, and reusable registration patterns.

Manage development, testing, staging, and production configuration without leaking secrets or hard-coding deployment values.

Prepare Flask for deployment with a WSGI entrypoint, Gunicorn, environment variables, process management, logging, and health checks.

Connect Flask to PostgreSQL with SQLAlchemy, environment database URLs, migrations, connection pooling, and production-safe query habits.

Serve CSS, JavaScript, images, and uploaded media efficiently with cache headers, hashed filenames, CDNs, and clean Flask template links.

Improve Flask response time with safe caching layers, cache keys, Redis-style stores, invalidation habits, and template fragment caching.

Understand when Flask work should move out of the request cycle and how Celery-style workers, queues, retries, and task status fit together.

Find Flask performance problems with measurement, query tuning, pagination, response size reduction, and request lifecycle awareness.

Build a small but production-shaped Flask blog with an app factory, blueprints, SQLAlchemy models, templates, forms, and publishing flow.

Build a small Flask JSON API with versioned blueprints, request validation, SQLAlchemy persistence, JSON errors, and curl-based testing.

Build a SaaS-style Flask dashboard shell with application layout, login-protected pages, organizations, settings, and extension points.

Recognize frequent Flask problems around globals, debug mode, database sessions, templates, forms, blueprints, and production readiness.

Understand the Flask extension ecosystem and decide when Flask is a strong fit compared with larger frameworks or async-first tools.

Choose a practical learning path after Flask: testing, databases, security, deployment, APIs, frontend integration, and system design.