Learn FastAPI by Examples
FastAPI 0.100+FastAPI is a modern, fast (high-performance), web framework for building APIs with Python 3.8+ based on standard Python type hints. It is designed to be easy to use and learn, while offering automatic validation and documentation generation.
These examples cover the core concepts of FastAPI development, focusing on how to leverage Pydantic models for data validation and how to define various types of API parameters efficiently.
Path Parameter Types
Path parameters are parts of the URL path that are variable. This sample code demonstrates how to define them with type hints to get automatic data validation and conversion.
Query Parameter Models
Query parameters are the key-value pairs that appear after the `?` in a URL. This code example shows how to define optional and required query parameters with default values.
Body Payload Models
Request bodies are used to send data from the client to the API. This example illustrates how to define a request body using Pydantic models for automatic validation and documentation.
Pydantic Field Types
Pydantic offers a rich set of specialized field types beyond standard Python types. This sample code shows how to use types like `EmailStr`, `HttpUrl`, and `UUID` for robust data validation.
Pydantic Validation Rules
Sometimes built-in types aren't enough. This code example demonstrates how to define custom validation logic using the `@field_validator` decorator to enforce complex business rules.
OAuth2 Bearer Schema
FastAPI provides built-in support for OAuth2, making it easy to implement secure authentication. This code example demonstrates how to set up the `OAuth2PasswordBearer` scheme to extract tokens.
Password Hashing Strategy
Storing passwords securely is non-negotiable. This code example demonstrates how to use PassLib with the bcrypt algorithm to hash passwords before saving them and verify them during login.
Header Parameter Extraction
Sometimes you need to read custom headers, such as API keys or user-agent strings. This sample code shows how to define and validate header parameters using the `Header` class.
Cookie Authentication Scheme
Cookies are often used for session management. This code example demonstrates how to read and write cookies securely using the `Cookie` parameter and `Response` object.
Custom Response Classes
While JSON is the default, sometimes you need to return other formats. This code example demonstrates how to use `HTMLResponse` and `PlainTextResponse` to return raw content.
File Response Handling
Serving files efficiently is a common requirement. This sample code shows how to use `FileResponse` to stream files from the server to the client asynchronously.
Streaming Response Output
For large datasets or continuous data streams, you don't want to wait for the entire response to be ready. This code example demonstrates how to use `StreamingResponse` to send data chunk by chunk.
Custom Response Classes
While JSON is the default, sometimes you need to return other formats. This code example demonstrates how to use `HTMLResponse` and `PlainTextResponse` to return raw content.
File Response Handling
Serving files efficiently is a common requirement. This sample code shows how to use `FileResponse` to stream files from the server to the client asynchronously.
Streaming Response Output
For large datasets or continuous data streams, you don't want to wait for the entire response to be ready. This code example demonstrates how to use `StreamingResponse` to send data chunk by chunk.
Redirect Response
Redirecting users to a different URL is a standard web pattern. This sample code shows how to use `RedirectResponse` to perform temporary or permanent redirects.