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Sebastián Ramírez
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<p align="center">
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<a href="https://fastapi.tiangolo.com"><img style="width: 70%;" src="img/logo-teal-vector.svg" alt='FastAPI'></a>
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</p>
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<p align="center">
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<em>FastAPI framework, high performance, easy to learn, fast to code, ready for production</em>
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</p>
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<p align="center">
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<a href="https://travis-ci.org/tiangolo/fastapi">
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<img src="https://travis-ci.org/tiangolo/fastapi.svg?branch=master" alt="Build Status">
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</a>
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<a href="https://codecov.io/gh/tiangolo/fastapi">
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<img src="https://codecov.io/gh/tiangolo/fastapi/branch/master/graph/badge.svg" alt="Coverage">
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</a>
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<a href="https://pypi.org/project/fastapi">
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<img src="https://badge.fury.io/py/fastapi.svg" alt="Package version">
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</a>
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</p>
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---
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**Documentation**: [https://fastapi.tiangolo.com](https://fastapi.tiangolo.com)
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---
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FastAPI is a modern, fast (high-performance), web framework for building APIs with Python 3.6+.
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The key features are:
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* **Fast**: Very high performance, on par with **NodeJS** and **Go** (thanks to Starlette and Pydantic).
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* **Intuitive**: Great editor support. <abbr title="also known as auto-complete, autocompletion, IntelliSense">Completion</abbr> everywhere. Less time debugging.
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* **Easy**: Designed to be easy to use and learn. Less time reading docs.
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* **Short**: Minimize code duplication. Multiple features from each parameter declaration.
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* **Robust**: Get production-ready code. With automatic interactive documentation.
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* **Standards-based**: Based on (and fully compatible with) the open standards for APIs: <a href="https://github.com/OAI/OpenAPI-Specification" target="_blank">OpenAPI</a> and <a href="http://json-schema.org/" target="_blank">JSON Schema</a>.
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## Requirements
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Python 3.6+
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FastAPI stands on the shoulders of giants:
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* <a href="https://www.starlette.io/" target="_blank">Starlette</a> for the web parts.
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* <a href="https://pydantic-docs.helpmanual.io/" target="_blank">Pydantic</a> for the data parts.
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## Installation
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```shell
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$ pip3 install fastapi
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```
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You will also need an ASGI server, for production such as <a href="http://www.uvicorn.org" target="_blank">uvicorn</a>.
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```shell
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$ pip3 install uvicorn
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```
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## Example
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* Create a file `main.py` with:
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```Python
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from fastapi import FastAPI
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app = FastAPI()
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@app.get('/')
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async def read_root():
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return {'hello': 'world'}
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```
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* Run the server with:
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```bash
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uvicorn main:app --debug
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```
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**Note**: the command `uvicorn main:app` refers to:
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* `main`: the file `main.py` (the Python "module").
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* `app`: the object created inside of `main.py` with the line `app = FastAPI()`.
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* `--debug`: make the server restart after code changes. Only use for development.
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### Check it
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Open your browser at <a href="http://127.0.0.1:8000" target="_blank">http://127.0.0.1:8000</a>.
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You will see the JSON response as:
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```JSON
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{"hello": "world"}
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```
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### Interactive API docs
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Now go to <a href="http://127.0.0.1:8000/docs" target="_blank">http://127.0.0.1:8000/docs</a>.
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You will see the automatic interactive API documentation (provided by <a href="https://github.com/swagger-api/swagger-ui" target="_blank">Swagger UI</a>):
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### Alternative API docs
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And now, go to <a href="http://127.0.0.1:8000/redoc" target="_blank">http://127.0.0.1:8000/redoc</a>.
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You will see the alternative automatic documentation (provided by <a href="https://github.com/Rebilly/ReDoc" target="_blank">ReDoc</a>):
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## Example upgrade
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Now modify the file `main.py` to include:
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* a path parameter `item_id`.
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* a body, declared using standard Python types (thanks to Pydantic).
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* an optional query parameter `q`.
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```Python
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from fastapi import FastAPI
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from pydantic import BaseModel
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app = FastAPI()
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class Item(BaseModel):
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name: str
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price: float
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is_offer: bool = None
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@app.get('/')
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async def read_root():
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return {'hello': 'world'}
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@app.post('/items/{item_id}')
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async def create_item(item_id: int, item: Item, q: str = None):
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return {"item_name": item.name, "item_id": item_id, "query": q}
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```
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The server should reload automatically (because you added `--debug` to the `uvicorn` command above).
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### Interactive API docs upgrade
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Now go to <a href="http://127.0.0.1:8000/docs" target="_blank">http://127.0.0.1:8000/docs</a>.
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* The interactive API documentation will be automatically updated, including the new query, and body:
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* Click on the button "Try it out", it allows you to fill the parameters and directly interact with the API:
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* 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:
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### Alternative API docs upgrade
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And now, go to <a href="http://127.0.0.1:8000/redoc" target="_blank">http://127.0.0.1:8000/redoc</a>.
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* The alternative documentation will also reflect the new query parameter and body:
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### Recap
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In summary, you declare **once** the types of parameters, body, etc. as function parameters. You don't have to learn a new syntax, use a specific library, class or object to declare fields, you just type standard Python types.
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For example, for an `int`:
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```Python
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item_id: int
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```
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or for a more complex `Item` model:
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```Python
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item: Item
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```
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...and with that single declaration you get:
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* Editor support, including:
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* Completion.
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* Type checks.
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* Validation of data:
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* Automatic and clear errors when the data is invalid.
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* Validation even for deeply nested JSON objects.
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* Serialization of input data: from the network to Python, reading from:
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* JSON.
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* Forms.
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* Files.
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* Path parameters.
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* Query parameters.
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* Cookies.
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* Headers.
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* Serialization of output data: from Python to network (as JSON):
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* Convert Python types (`str`, `int`, `float`, `bool`, `list`, etc).
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* `datetime` objects.
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* `UUID` objects.
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* Database models.
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* ...and many more.
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* Automatic interactive API documentation, including 2 alternative user interfaces:
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* Swagger UI.
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* ReDoc.
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---
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Coming back to the previous code example, **FastAPI** will:
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* Validate that there is an `item_id` in the path.
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* Validate that the `item_id` is of type `int`. If it is not, the client will see a useful error.
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* Check if there is an optional query parameter named `q` (as in `http://127.0.0.1:8000/items/foo?q=somequery`). As the `q` parameter is declared with `= None`, it is optional. Without the `None` it would be required (as is the body).
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* Read the body as JSON:
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* Check that it has a required attribute `name` that should be a `str`.
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* Check that is has a required attribute `price` that has to be a `float`.
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* Check that it has an optional attribute `is_offer`, that should be a `bool`, if present.
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* All this would also work for deeply nested JSON objects
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* Convert from and to JSON automatically.
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* Document everything as OpenAPI, so the interactive documentation is created and updated automatically.
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* Provide the interactive documentation web interfaces.
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---
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We just scratched the surface, but you already get the idea of how it all works.
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Try changing the line with:
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```Python
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return {"item_name": item.name, "item_id": item_id, "query": q}
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```
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...from:
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```Python
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... "item_name": item.name ...
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```
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...to:
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```Python
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... "item_price": item.price ...
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```
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...and see how your editor will auto-complete the attributes and know their types:
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For a more complete example including more features, [see the tutorial](tutorial).
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**Spoiler alert**: the tutorial, although very short, includes:
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* Declaration of **parameters** from different places as: headers, cookies, form data and files.
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* How to set **validation constrains** as `maximum_length` or `regex`.
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* A very powerful and easy to use **Dependency Injection** system (also known as "components", "resources", "providers", "services").
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* Security and authentication, including support for **OAuth2** with **JWT tokens** and **HTTP Basic** auth.
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* More advanced (but equally easy) techniques for declaring **deeply nested models** (JSON body, Form and Files) (thanks to Pydantic).
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* Many extra features (thanks to Starlette) as **WebSockets**, **GraphQL**, extremely easy tests based on `requests` and `pytest`, CORS, Cookie Sessions and more.
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## Optional Dependencies
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Used by Pydantic:
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* <a href="https://github.com/esnme/ultrajson" target="_blank"><code>ujson</code></a> - for faster JSON parsing.
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* <a href="https://github.com/JoshData/python-email-validator" target="_blank"><code>email_validator</code></a> - for email validation.
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Used by Starlette:
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* <a href="http://docs.python-requests.org" target="_blank"><code>requests</code></a> - Required if you want to use the `TestClient`.
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* <a href="https://github.com/Tinche/aiofiles" target="_blank"><code>aiofiles</code></a> - Required if you want to use `FileResponse` or `StaticFiles`.
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* <a href="http://jinja.pocoo.org" target="_blank"><code>jinja2</code></a> - Required if you want to use the default template configuration.
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* <a href="https://andrew-d.github.io/python-multipart/" target="_blank"><code>python-multipart</code></a> - Required if you want to support form parsing, with `request.form()`.
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* <a href="https://pythonhosted.org/itsdangerous/" target="_blank"><code>itsdangerous</code></a> - Required for `SessionMiddleware` support.
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* <a href="https://pyyaml.org/wiki/PyYAMLDocumentation" target="_blank"><code>pyyaml</code></a> - Required for `SchemaGenerator` support.
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* <a href="https://graphene-python.org/" target="_blank"><code>graphene</code></a> - Required for `GraphQLApp` support.
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* <a href="https://github.com/esnme/ultrajson" target="_blank"><code>ujson</code></a> - Required if you want to use `UJSONResponse`.
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You can install all of these with `pip3 install fastapi[full]`.
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## License
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This project is licensed under the terms of the MIT license.
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