Github url

fastapi

by tiangolo

tiangolo /fastapi

FastAPI framework, high performance, easy to learn, fast to code, ready for production

19.3K Stars 1.3K Forks Last release: 16 days ago (0.60.1) MIT License 1.2K Commits 97 Releases

Available items

No Items, yet!

The developer of this repository has not created any items for sale yet. Need a bug fixed? Help with integration? A different license? Create a request here:

FastAPI

FastAPI framework, high performance, easy to learn, fast to code, ready for production

TestCoveragePackage versionJoin the chat at https://gitter.im/tiangolo/fastapi


Documentation: https://fastapi.tiangolo.com

Source Code: https://github.com/tiangolo/fastapi


FastAPI is a modern, fast (high-performance), web framework for building APIs with Python 3.6+ based on standard Python type hints.

The key features are:

  • Fast: Very high performance, on par with NodeJS and Go (thanks to Starlette and Pydantic). One of the fastest Python frameworks available.

  • Fast to code: Increase the speed to develop features by about 200% to 300%. *

  • Fewer bugs: Reduce about 40% of human (developer) induced errors. *

  • Intuitive: Great editor support. Completion everywhere. Less time debugging.

  • Easy: Designed to be easy to use and learn. Less time reading docs.

  • Short: Minimize code duplication. Multiple features from each parameter declaration. Fewer bugs.

  • Robust: Get production-ready code. With automatic interactive documentation.

  • Standards-based: Based on (and fully compatible with) the open standards for APIs: OpenAPI (previously known as Swagger) and JSON Schema.

* estimation based on tests on an internal development team, building production applications.

Opinions

"[...] I'm using FastAPI a ton these days. [...] I'm actually planning to use it for all of my team's ML services at Microsoft. Some of them are getting integrated into the core Windows product and some Office products."

Kabir Khan - Microsoft (ref)


"We adopted the FastAPI library to spawn a REST server that can be queried to obtain predictions. [for Ludwig]"

Piero Molino, Yaroslav Dudin, and Sai Sumanth Miryala - Uber (ref)


"Netflix is pleased to announce the open-source release of our crisis management orchestration framework: Dispatch! [built with FastAPI]"

Kevin Glisson, Marc Vilanova, Forest Monsen - Netflix (ref)


"I’m over the moon excited about FastAPI. It’s so fun!"

Brian Okken - Python Bytes podcast host (ref)


"Honestly, what you've built looks super solid and polished. In many ways, it's what I wanted Hug to be - it's really inspiring to see someone build that."

Timothy Crosley - Hug creator (ref)


"If you're looking to learn one modern framework for building REST APIs, check out FastAPI [...] It's fast, easy to use and easy to learn [...]"

"We've switched over to FastAPI for our APIs [...] I think you'll like it [...]"

Ines Montani - Matthew Honnibal - Explosion AI founders - spaCy creators (ref) - (ref)


Typer, the FastAPI of CLIs

If you are building a CLI app to be used in the terminal instead of a web API, check out Typer.

Typer is FastAPI's little sibling. And it's intended to be the FastAPI of CLIs. ⌨️ 🚀

Requirements

Python 3.6+

FastAPI stands on the shoulders of giants:

Installation

console $ pip install fastapi ---\> 100%

You will also need an ASGI server, for production such as Uvicorn or Hypercorn.

console $ pip install uvicorn ---\> 100%

Example

Create it

  • Create a file
    main.py
    with:
from typing import Optional from fastapi import FastAPI app = FastAPI() @app.get("/") def read\_root(): return {"Hello": "World"} @app.get("/items/{item\_id}") def read\_item(item\_id: int, q: Optional[str] = None): return {"item\_id": item\_id, "q": q}
Or use async def...

If your code uses async / await, use async def:

from typing import Optional

from fastapi import FastAPI

app = FastAPI()

@app.get("/")
async def read_root():
    return {"Hello": "World"}

@app.get("/items/{item_id}")
async def read_item(item_id: int, q: Optional[str] = None):
    return {"item_id": item_id, "q": q}

Note:

If you don't know, check the "In a hurry?" section about async and await in the docs.

### Run it

Run the server with:

console $ uvicorn main:app --reload INFO: Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit) INFO: Started reloader process [28720] INFO: Started server process [28722] INFO: Waiting for application startup. INFO: Application startup complete.

About the command uvicorn main:app --reload...

The command uvicorn main:app refers to:

  • main: the file main.py (the Python "module").
  • app: the object created inside of main.py with the line app = FastAPI().
  • --reload: make the server restart after code changes. Only do this for development.
### Check it

Open your browser at http://127.0.0.1:8000/items/5?q=somequery.

You will see the JSON response as:

{"item\_id": 5, "q": "somequery"}

You already created an API that:

  • Receives HTTP requests in the paths
    /
    and
    /items/{item\_id}
    .
  • Both paths take
    GET
    operations (also known as HTTP methods).
  • The path
    /items/{item\_id}
    has a path parameter
    item\_id
    that should be an
    int
    .
  • The path
    /items/{item\_id}
    has an optional
    str
    query parameter
    q
    .

Interactive API docs

Now go to http://127.0.0.1:8000/docs.

You will see the automatic interactive API documentation (provided by Swagger UI):

Swagger UI

Alternative API docs

And now, go to http://127.0.0.1:8000/redoc.

You will see the alternative automatic documentation (provided by ReDoc):

ReDoc

Example upgrade

Now modify the file

main.py

to receive a body from a

PUT

request.

Declare the body using standard Python types, thanks to Pydantic.


from fastapi import FastAPI from pydantic import BaseModel

app = FastAPI()

class Item(BaseModel): name: str price: float is\_offer: Optional[bool] = None

@app.get("/") def read\_root(): return {"Hello": "World"}

@app.get("/items/{item_id}") def read_item(item_id: int, q: Optional[str] = None): return {"item_id": item\_id, "q": q}

@app.put("/items/{item_id}") def update_item(item_id: int, item: Item): return {"item_name": item.name, "item_id": item_id} ```

The server should reload automatically (because you added

--reload

 to the 

uvicorn

 command above).
### Interactive API docs upgrade

Now go to [http://127.0.0.1:8000/docs](http://127.0.0.1:8000/docs).

- The interactive API documentation will be automatically updated, including the new body:

![Swagger UI](https://fastapi.tiangolo.com/img/index/index-03-swagger-02.png)

- Click on the button "Try it out", it allows you to fill the parameters and directly interact with the API:

![Swagger UI interaction](https://fastapi.tiangolo.com/img/index/index-04-swagger-03.png)

- Then click on the "Execute" button, the user interface will communicate with your API, send the parameters, get the results and show them on the screen:

![Swagger UI interaction](https://fastapi.tiangolo.com/img/index/index-05-swagger-04.png)

### Alternative API docs upgrade

And now, go to [http://127.0.0.1:8000/redoc](http://127.0.0.1:8000/redoc).

- The alternative documentation will also reflect the new query parameter and body:

![ReDoc](https://fastapi.tiangolo.com/img/index/index-06-redoc-02.png)

### Recap

In summary, you declare **once** the types of parameters, body, etc. as function parameters.

You do that with standard modern Python types.

You don't have to learn a new syntax, the methods or classes of a specific library, etc.

Just standard **Python 3.6+**.

For example, for an

int

:

item_id: int


or for a more complex

Item

 model:

item: Item


...and with that single declaration you get:

- Editor support, including:
  - Completion.
  - Type checks.
- Validation of data:
  - Automatic and clear errors when the data is invalid.
  - Validation even for deeply nested JSON objects.
- <abbr title="also known as: serialization, parsing, marshalling">Conversion</abbr> of input data: coming from the network to Python data and types. Reading from:
  - JSON.
  - Path parameters.
  - Query parameters.
  - Cookies.
  - Headers.
  - Forms.
  - Files.
- <abbr title="also known as: serialization, parsing, marshalling">Conversion</abbr> of output data: converting from Python data and types to network data (as JSON):
  - Convert Python types (

str

, 

int

, 

float

, 

bool

, 

list

, etc).
  - 

datetime

 objects.
  - 

UUID

 objects.
  - Database models.
  - ...and many more.
- Automatic interactive API documentation, including 2 alternative user interfaces:
  - Swagger UI.
  - ReDoc.

* * *

Coming back to the previous code example, **FastAPI** will:

- Validate that there is an 

item_id

 in the path for 

GET

 and 

PUT

 requests.
- Validate that the 

item_id

 is of type 

int

 for 

GET

 and 

PUT

 requests.
  - If it is not, the client will see a useful, clear error.
- Check if there is an optional query parameter named 

q

 (as in 

http://127.0.0.1:8000/items/foo?q=somequery

) for 

GET

 requests.
  - As the 

q

 parameter is declared with 

= None

, it is optional.
  - Without the 

None

 it would be required (as is the body in the case with 

PUT

).
- For 

PUT

 requests to 

/items/{item_id}

, Read the body as JSON:
  - Check that it has a required attribute 

name

 that should be a 

str

. 
  - Check that it has a required attribute 

price

 that has to be a 

float

.
  - Check that it has an optional attribute 

is_offer

, that should be a 

bool

, if present.
  - All this would also work for deeply nested JSON objects.
- Convert from and to JSON automatically.
- Document everything with OpenAPI, that can be used by:
  - Interactive documentation systems.
  - Automatic client code generation systems, for many languages.
- Provide 2 interactive documentation web interfaces directly.

* * *

We just scratched the surface, but you already get the idea of how it all works.

Try changing the line with:

return {"item_name": item.name, "item_id": item_id}


...from:

... "item_name": item.name ...


...to:

... "item_price": item.price ...


...and see how your editor will auto-complete the attributes and know their types:

![editor support](https://fastapi.tiangolo.com/img/vscode-completion.png)

For a more complete example including more features, see the [Tutorial - User Guide](https://fastapi.tiangolo.com/tutorial/).

**Spoiler alert**: the tutorial - user guide includes:

- Declaration of **parameters** from other different places as: **headers**, **cookies**, **form fields** and **files**.
- How to set **validation constraints** as 

maximum_length

 or 

regex

.
- A very powerful and easy to use **<abbr title="also known as components, resources, providers, services, injectables">Dependency Injection</abbr>** system.
- Security and authentication, including support for **OAuth2** with **JWT tokens** and **HTTP Basic** auth.
- More advanced (but equally easy) techniques for declaring **deeply nested JSON models** (thanks to Pydantic).
- Many extra features (thanks to Starlette) as:
  - **WebSockets**
  - **GraphQL**
  - extremely easy tests based on 

requests

 and 

pytest

  - **CORS**
  - **Cookie Sessions**
  - ...and more.

## Performance

Independent TechEmpower benchmarks show **FastAPI** applications running under Uvicorn as [one of the fastest Python frameworks available](https://www.techempower.com/benchmarks/#section=test&runid=7464e520-0dc2-473d-bd34-dbdfd7e85911&hw=ph&test=query&l=zijzen-7), only below Starlette and Uvicorn themselves (used internally by FastAPI). (\*)

To understand more about it, see the section [Benchmarks](https://fastapi.tiangolo.com/benchmarks/).

## Optional Dependencies

Used by Pydantic:

- [`ujson`](https://github.com/esnme/ultrajson) - for faster JSON <abbr title="converting the string that comes from an HTTP request into Python data">"parsing"</abbr>.
- [`email_validator`](https://github.com/JoshData/python-email-validator) - for email validation.

Used by Starlette:

- [`requests`](http://docs.python-requests.org) - Required if you want to use the 

TestClient

.
- [`aiofiles`](https://github.com/Tinche/aiofiles) - Required if you want to use 

FileResponse

 or 

StaticFiles

.
- [`jinja2`](http://jinja.pocoo.org) - Required if you want to use the default template configuration.
- [`python-multipart`](https://andrew-d.github.io/python-multipart/) - Required if you want to support form <abbr title="converting the string that comes from an HTTP request into Python data">"parsing"</abbr>, with 

request.form()

.
- [`itsdangerous`](https://pythonhosted.org/itsdangerous/) - Required for 

SessionMiddleware

 support.
- [`pyyaml`](https://pyyaml.org/wiki/PyYAMLDocumentation) - Required for Starlette's 

SchemaGenerator

 support (you probably don't need it with FastAPI).
- [`graphene`](https://graphene-python.org/) - Required for 

GraphQLApp

 support.
- [`ujson`](https://github.com/esnme/ultrajson) - Required if you want to use 

UJSONResponse

.

Used by FastAPI / Starlette:

- [`uvicorn`](http://www.uvicorn.org) - for the server that loads and serves your application.
- [`orjson`](https://github.com/ijl/orjson) - Required if you want to use 

ORJSONResponse

.

You can install all of these with

pip install fastapi[all]

``` .

License

This project is licensed under the terms of the MIT license.

We use cookies. If you continue to browse the site, you agree to the use of cookies. For more information on our use of cookies please see our Privacy Policy.