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](#performance).
* **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. <abbrtitle="also known as auto-complete, autocompletion, IntelliSense">Completion</abbr> 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: <ahref="https://github.com/OAI/OpenAPI-Specification"class="external-link"target="_blank">OpenAPI</a> (previously known as Swagger) and <ahref="https://json-schema.org/"class="external-link"target="_blank">JSON Schema</a>.
<small>* estimation based on tests on an internal development team, building production applications.</small>
"_[...] 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._"
"_We adopted the **FastAPI** library to spawn a **REST** server that can be queried to obtain **predictions**. [for Ludwig]_"
<divstyle="text-align: right; margin-right: 10%;">Piero Molino, Yaroslav Dudin, and Sai Sumanth Miryala - <strong>Uber</strong><ahref="https://eng.uber.com/ludwig-v0-2/"target="_blank"><small>(ref)</small></a></div>
---
"_**Netflix** is pleased to announce the open-source release of our **crisis management** orchestration framework: **Dispatch**! [built with **FastAPI**]_"
"_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._"
"_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 [...]_"
If you are building a <abbrtitle="Command Line Interface">CLI</abbr> app to be used in the terminal instead of a web API, check out <ahref="https://typer.tiangolo.com/"class="external-link"target="_blank">**Typer**</a>.
**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:
* <ahref="https://www.starlette.io/"class="external-link"target="_blank">Starlette</a> for the web parts.
* <ahref="https://pydantic-docs.helpmanual.io/"class="external-link"target="_blank">Pydantic</a> for the data parts.
## Installation
<divclass="termy">
```console
$ pip install fastapi
---> 100%
```
</div>
You will also need an ASGI server, for production such as <ahref="https://www.uvicorn.org"class="external-link"target="_blank">Uvicorn</a> or <ahref="https://gitlab.com/pgjones/hypercorn"class="external-link"target="_blank">Hypercorn</a>.
If you don't know, check the _"In a hurry?"_ section about <ahref="https://fastapi.tiangolo.com/async/#in-a-hurry"target="_blank">`async` and `await` in the docs</a>.
</details>
### Run it
Run the server with:
<divclass="termy">
```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.
```
</div>
<detailsmarkdown="1">
<summary>About the command <code>uvicorn main:app --reload</code>...</summary>
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.
</details>
### Check it
Open your browser at <ahref="http://127.0.0.1:8000/items/5?q=somequery"class="external-link"target="_blank">http://127.0.0.1:8000/items/5?q=somequery</a>.
You will see the JSON response as:
```JSON
{"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`<em>operations</em> (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 <ahref="http://127.0.0.1:8000/docs"class="external-link"target="_blank">http://127.0.0.1:8000/docs</a>.
You will see the automatic interactive API documentation (provided by <ahref="https://github.com/swagger-api/swagger-ui"class="external-link"target="_blank">Swagger UI</a>):
And now, go to <ahref="http://127.0.0.1:8000/redoc"class="external-link"target="_blank">http://127.0.0.1:8000/redoc</a>.
You will see the alternative automatic documentation (provided by <ahref="https://github.com/Rebilly/ReDoc"class="external-link"target="_blank">ReDoc</a>):
* 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:
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`:
```Python
item_id: int
```
or for a more complex `Item` model:
```Python
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.
* <abbrtitle="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.
* <abbrtitle="also known as: serialization, parsing, marshalling">Conversion</abbr> of output data: converting from Python data and types to network data (as JSON):
For a more complete example including more features, see the <ahref="https://fastapi.tiangolo.com/tutorial/">Tutorial - User Guide</a>.
**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 **<abbrtitle="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 <ahref="https://www.techempower.com/benchmarks/#section=test&runid=7464e520-0dc2-473d-bd34-dbdfd7e85911&hw=ph&test=query&l=zijzen-7"class="external-link"target="_blank">one of the fastest Python frameworks available</a>, only below Starlette and Uvicorn themselves (used internally by FastAPI). (*)
To understand more about it, see the section <ahref="https://fastapi.tiangolo.com/benchmarks/"class="internal-link"target="_blank">Benchmarks</a>.
## Optional Dependencies
Used by Pydantic:
* <ahref="https://github.com/esnme/ultrajson"target="_blank"><code>ujson</code></a> - for faster JSON <abbrtitle="converting the string that comes from an HTTP request into Python data">"parsing"</abbr>.
* <ahref="https://github.com/JoshData/python-email-validator"target="_blank"><code>email_validator</code></a> - for email validation.
Used by Starlette:
* <ahref="https://requests.readthedocs.io"target="_blank"><code>requests</code></a> - Required if you want to use the `TestClient`.
* <ahref="https://github.com/Tinche/aiofiles"target="_blank"><code>aiofiles</code></a> - Required if you want to use `FileResponse` or `StaticFiles`.
* <ahref="https://jinja.palletsprojects.com"target="_blank"><code>jinja2</code></a> - Required if you want to use the default template configuration.
* <ahref="https://andrew-d.github.io/python-multipart/"target="_blank"><code>python-multipart</code></a> - Required if you want to support form <abbrtitle="converting the string that comes from an HTTP request into Python data">"parsing"</abbr>, with `request.form()`.
* <ahref="https://pythonhosted.org/itsdangerous/"target="_blank"><code>itsdangerous</code></a> - Required for `SessionMiddleware` support.
* <ahref="https://pyyaml.org/wiki/PyYAMLDocumentation"target="_blank"><code>pyyaml</code></a> - Required for Starlette's `SchemaGenerator` support (you probably don't need it with FastAPI).
* <ahref="https://graphene-python.org/"target="_blank"><code>graphene</code></a> - Required for `GraphQLApp` support.
* <ahref="https://github.com/esnme/ultrajson"target="_blank"><code>ujson</code></a> - Required if you want to use `UJSONResponse`.
Used by FastAPI / Starlette:
* <ahref="https://www.uvicorn.org"target="_blank"><code>uvicorn</code></a> - for the server that loads and serves your application.
* <ahref="https://github.com/ijl/orjson"target="_blank"><code>orjson</code></a> - 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.
Nasaruddin
GitHub