6.3. FastAPI Architecture

  • Uvicorn

  • Starlette

  • Pydantic

  • Type Annotations

../../_images/fastapi-architecture.png

6.3.1. Standard WSGI

  • WSGI - Web Server Gateway Interface

6.3.2. Standard ASGI

ASGI (Asynchronous Server Gateway Interface) is a spiritual successor to WSGI, intended to provide a standard interface between async-capable Python web servers, frameworks, and applications.

Where WSGI provided a standard for synchronous Python apps, ASGI provides one for both asynchronous and synchronous apps, with a WSGI backwards-compatibility implementation and multiple servers and application frameworks.

6.3.3. Uvicorn

  • Uvicorn is a lightning-fast ASGI server implementation, using uvloop and httptools.

  • Until recently Python has lacked a minimal low-level server/application interface for asyncio frameworks. The ASGI specification fills this gap, and means we're now able to start building a common set of tooling usable across all asyncio frameworks.

  • ASGI should help enable an ecosystem of Python web frameworks that are highly competitive against Node and Go in terms of achieving high throughput in IO-bound contexts. It also provides support for HTTP/2 and WebSockets, which cannot be handled by WSGI.

  • Uvicorn currently supports HTTP/1.1 and WebSockets. Support for HTTP/2 is planned.

Source: 1

6.3.4. Starlette

  • Starlette is a lightweight ASGI framework/toolkit, which is ideal for building high performance asyncio services.

  • It is production-ready

  • Seriously impressive performance

  • WebSocket support

  • GraphQL support

  • In-process background tasks

  • Startup and shutdown events

  • Test client built on requests

  • CORS, GZip, Static Files, Streaming responses

  • Session and Cookie support

  • 100% test coverage

  • 100% type annotated codebase

  • Zero hard dependencies

Source: 3

6.3.5. Pydantic

  • Data validation and settings management using python type annotations.

  • pydantic enforces type hints at runtime, and provides user friendly errors when data is invalid.

  • Define how data should be in pure, canonical python; validate it with pydantic.

  • There's no new schema definition micro-language to learn

  • pydantic's BaseSettings class allows pydantic to be used in both a "validate this request data" context and in a "load my system settings" context

  • In benchmarks pydantic is faster than all other tested libraries

  • validate complex structures

  • pydantic allows custom data types to be defined or you can extend validation with methods on a model decorated with the validator decorator.

  • dataclasses integration

Source: 2

6.3.6. References

1

Uvicorn official documentation. Year: 2021. Retrieved: 2021-02-23. URL: https://www.uvicorn.org

2

Pydantic official documentation. Year: 2021. Retrieved: 2021-02-23. URL: https://pydantic-docs.helpmanual.io

3

Starlette official documentation. Year: 2021. Retrieved: 2021-02-23. URL: https://www.starlette.io