fastapi 0.58.0

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

Documentation:https://fastapi.tiangolo

Source Code:https://github /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 withNodeJSandGo(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.Completioneverywhere. 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) andJSON Schema.

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

Opinions

"[...] I'm usingFastAPIa ton these days. [...] I'm actually planning to use it for all of my team'sML services at Microsoft.Some of them are getting integrated into the coreWindowsproduct and someOfficeproducts."

"We adopted theFastAPIlibrary to spawn aRESTserver that can be queried to obtainpredictions.[for Ludwig]"

"Netflixis pleased to announce the open-source release of ourcrisis managementorchestration framework:Dispatch![built withFastAPI]"

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

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

"If you're looking to learn onemodern frameworkfor building REST APIs, check outFastAPI[...] It's fast, easy to use and easy to learn [...]"

"We've switched over toFastAPIfor ourAPIs[...] I think you'll like it [...]"

Typer,the FastAPI of CLIs

If you are building aCLIapp to be used in the terminal instead of a web API, check outTyper.

Typeris FastAPI's little sibling. And it's intended to be theFastAPI of CLIs.⌨️ 🚀

Requirements

Python 3.6+

FastAPI stands on the shoulders of giants:

• Starlettefor the web parts.
• Pydanticfor the data parts.

Installation

$pipinstallfastapi

---> 100%

You will also need an ASGI server, for production such asUvicornorHypercorn.

$pipinstalluvicorn

---> 100%

Example

Create it

• Create a filemain.pywith:

fromfastapiimportFastAPI

app=FastAPI()


@app.get("/")
defread_root():
return{"Hello":"World"}


@app.get("/items/{item_id}")
defread_item(item_id:int,q:str=None):
return{"item_id":item_id,"q":q}

fromfastapiimportFastAPI

app=FastAPI()


@app.get("/")
asyncdefread_root():
return{"Hello":"World"}


@app.get("/items/{item_id}")
asyncdefread_item(item_id:int,q:str=None):
return{"item_id":item_id,"q":q}

Run it

Run the server with:

$uvicornmain: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.

Check it

Open your browser athttp://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 thepaths/and/items/{item_id}.
• BothpathstakeGEToperations(also known as HTTPmethods).
• Thepath/items/{item_id}has apath parameteritem_idthat should be anint.
• Thepath/items/{item_id}has an optionalstrquery parameterq.

Interactive API docs

Now go tohttp://127.0.0.1:8000/docs.

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

Alternative API docs

And now, go tohttp://127.0.0.1:8000/redoc.

You will see the alternative automatic documentation (provided byReDoc):

Example upgrade

Now modify the filemain.pyto receive a body from aPUTrequest.

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

fromfastapiimportFastAPI
frompydanticimportBaseModel

app=FastAPI()


classItem(BaseModel):
name:str
price:float
is_offer:bool=None


@app.get("/")
defread_root():
return{"Hello":"World"}


@app.get("/items/{item_id}")
defread_item(item_id:int,q:str=None):
return{"item_id":item_id,"q":q}


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

The server should reload automatically (because you added--reloadto theuvicorncommand above).

Interactive API docs upgrade

Now go tohttp://127.0.0.1:8000/docs.

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

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

• 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:

Alternative API docs upgrade

And now, go tohttp://127.0.0.1:8000/redoc.

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

Recap

In summary, you declareoncethe 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 standardPython 3.6+.

For example, for anint:

item_id:int

or for a more complexItemmodel:

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.
• Conversionof input data: coming from the network to Python data and types. Reading from:
  • JSON.
  • Path parameters.
  • Query parameters.
  • Cookies.
  • Headers.
  • Forms.
  • Files.
• Conversionof output data: converting from Python data and types to network data (as JSON):
  • Convert Python types (str,int,float,bool,list,etc).
  • datetimeobjects.
  • UUIDobjects.
  • Database models.
  • ...and many more.
• Automatic interactive API documentation, including 2 alternative user interfaces:
  • Swagger UI.
  • ReDoc.

Coming back to the previous code example,FastAPIwill:

• Validate that there is anitem_idin the path forGETandPUTrequests.
• Validate that theitem_idis of typeintforGETandPUTrequests.
  • If it is not, the client will see a useful, clear error.
• Check if there is an optional query parameter namedq(as inhttp://127.0.0.1:8000/items/foo?q=somequery) forGETrequests.
  • As theqparameter is declared with= None,it is optional.
  • Without theNoneit would be required (as is the body in the case withPUT).
• ForPUTrequests to/items/{item_id},Read the body as JSON:
  • Check that it has a required attributenamethat should be astr.
  • Check that it has a required attributepricethat has to be afloat.
  • Check that it has an optional attributeis_offer,that should be abool,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:

For a more complete example including more features, see theTutorial - User Guide.

Spoiler alert:the tutorial - user guide includes:

• Declaration ofparametersfrom other different places as:headers,cookies,form fieldsandfiles.
• How to setvalidation constraintsasmaximum_lengthorregex.
• A very powerful and easy to useDependency Injectionsystem.
• Security and authentication, including support forOAuth2withJWT tokensandHTTP Basicauth.
• More advanced (but equally easy) techniques for declaringdeeply nested JSON models(thanks to Pydantic).
• Many extra features (thanks to Starlette) as:
  • WebSockets
  • GraphQL
  • extremely easy tests based onrequestsandpytest
  • CORS
  • Cookie Sessions
  • ...and more.

Performance

Independent TechEmpower benchmarks showFastAPIapplications running under Uvicorn asone of the fastest Python frameworks available,only below Starlette and Uvicorn themselves (used internally by FastAPI). (*)

To understand more about it, see the sectionBenchmarks.

Optional Dependencies

Used by Pydantic:

• ujson- for faster JSON"parsing".
• email_validator- for email validation.

Used by Starlette:

• requests- Required if you want to use theTestClient.
• aiofiles- Required if you want to useFileResponseorStaticFiles.
• jinja2- Required if you want to use the default template configuration.
• Python -multipart- Required if you want to support form"parsing",withrequest.form().
• itsdangerous- Required forSessionMiddlewaresupport.
• pyyaml- Required for Starlette'sSchemaGeneratorsupport (you probably don't need it with FastAPI).
• graphene- Required forGraphQLAppsupport.
• ujson- Required if you want to useUJSONResponse.

Used by FastAPI / Starlette:

• uvicorn- for the server that loads and serves your application.
• orjson- Required if you want to useORJSONResponse.

You can install all of these withpip install fastapi[all].

License

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