Python INTERMEDIATEFastAPI
Modern, fast web framework for building APIs with Python type hints
10 min read
fastapipythonapiasyncrestweb
Table of Contents
Getting Started
Installation and basic setup
Installation & Setup
Install FastAPI and create your first app
bash
💡 FastAPI is based on Python type hints and async/await
⚡ Automatic API documentation with Swagger UI
📌 Built on Starlette (web) and Pydantic (data)
🟢 Production-ready with uvicorn ASGI server
installationsetup
Basic Application
Create your first FastAPI application
python
💡 FastAPI automatically generates OpenAPI docs
⚡ Access Swagger UI at /docs endpoint
📌 Async functions provide better performance
🟢 CORS middleware needed for browser requests
basicshello-world
Path Parameters
Dynamic URL segments with type validation
python
💡 Path parameters are automatically validated
⚡ Type conversion happens automatically
📌 Use Enum for predefined path values
🟢 Path parameters are always required
routingparameters
Query Parameters
URL query strings and optional parameters
python
💡 Non-path parameters become query parameters
⚡ Use Optional or defaults for optional params
📌 Query() adds validation and documentation
🟢 Lists and complex types are supported
queryparameters
Request & Response Models
Data validation with Pydantic
Pydantic Models
Define and validate data structures
python
💡 Automatic request/response validation
⚡ Type hints provide IDE support
📌 Field() adds validation constraints
🟢 JSON Schema generated for API docs
pydanticvalidation
Request Body
Handle complex request data
python
💡 Automatic JSON parsing and validation
⚡ Combine body, path, and query params
📌 Support for forms and file uploads
🟢 UploadFile for efficient file handling
requestbodyforms
Response Models
Control response data structure
python
💡 Separate input/output models for security
⚡ Automatic serialization to JSON
📌 Filter sensitive fields from responses
🟢 Support for lists and unions
responsemodels
Status Codes
HTTP status codes and headers
python
💡 Use status module for standard codes
⚡ Set custom headers in responses
📌 Different status for different scenarios
🟢 Read and write headers easily
statusheaders
Dependencies & Security
Dependency injection and authentication
Dependency Injection
Reusable dependencies and shared logic
python
💡 Share logic between multiple endpoints
⚡ Automatic dependency resolution
📌 Support for nested dependencies
🟢 Great for auth and database sessions
dependenciesDI
OAuth2 Authentication
JWT tokens and password hashing
python
💡 Built-in OAuth2 password flow support
⚡ JWT for stateless authentication
🔐 Secure password hashing with bcrypt
🟢 Integrate with any auth provider
authoauth2jwt
CORS Middleware
Cross-Origin Resource Sharing setup
python
💡 Enable cross-origin browser requests
⚡ Configure allowed origins and methods
📌 Support credentials and preflight
🟢 Essential for frontend separation
corsmiddleware
Error Handling
Custom error responses and exceptions
python
💡 HTTPException for standard errors
⚡ Custom exception handlers for control
📌 Global handlers for unhandled errors
🟢 Include helpful error details
errorsexceptions
Database Integration
Working with databases in FastAPI
SQLAlchemy Setup
Database ORM configuration
python
💡 SQLAlchemy for ORM functionality
⚡ Connection pooling built-in
📌 Works with PostgreSQL, MySQL, SQLite
🟢 Use dependency for session management
databasesqlalchemy
Database Models
Define database tables as classes
python
💡 Models define database structure
⚡ Relationships handle joins automatically
📌 Indexes improve query performance
🟢 Migrations with Alembic recommended
modelsorm
CRUD Operations
Database operations with dependency injection
python
💡 Separate CRUD logic from routes
⚡ Use transactions for data consistency
📌 Always refresh after create/update
🟢 Handle errors with try/except blocks
cruddatabase
Async SQLAlchemy
Asynchronous database operations
python
💡 Better performance with async/await
⚡ Non-blocking database queries
📌 Use asyncpg for PostgreSQL
🟢 Same ORM features, async execution
asyncdatabase
Advanced Features
WebSockets, background tasks, and testing
Background Tasks
Run tasks after returning response
python
💡 Execute tasks after sending response
⚡ Don't block response for slow operations
📌 Great for emails and notifications
🟢 Use Celery for complex task queues
backgroundasync
WebSockets
Real-time bidirectional communication
python
💡 Full-duplex communication channels
⚡ Real-time updates and notifications
📌 Perfect for chat and live feeds
🟢 Built on Starlette WebSocket support
websocketrealtime
Testing
Test FastAPI applications
python
💡 Built-in test client based on httpx
⚡ Support for async test functions
📌 Test auth and dependencies easily
🟢 Integration with pytest framework
testingpytest
API Documentation
Automatic interactive documentation
python
💡 Automatic OpenAPI/Swagger generation
⚡ Interactive docs at /docs endpoint
📌 ReDoc alternative at /redoc
🟢 Customizable metadata and examples
documentationopenapi