fastapi

Installation

pip install fastapi[all] uvicorn[standard]

Test to see if it installed successfully

>>> from fastapi import FastAPI
>>> app = FastAPI()
>>> app
<fastapi.applications.FastAPI object at 0x107040c70>

Query Method

• HTTP methods
  • common
    • GET
    • POST
    • PUT
    • DELETE
  • exotic ones
    • OPTIONS
    • HEAD
    • PATCH
    • TRACE

@app.post('/route')
@app.get('/route')
def route_controller():
    return {'msg' : 'Im route'}

Path Parameters

@app.get('/items/{item_id}')
async def read_item(item_id: int):
    return {'item_id': item_id}

Enum

from enum import Enum

class TypeName(str, Enum):
    type_a = 'A'
    type_b = 'B'
    type_c = 'C'

@app.get('/types/{type_name}')
async def get_type(type_name: TypeName):
    return {'type_name': type_name}

File Path

@app.get("/files/{file_path:path}")
async def read_file(file_path: str):
    return {"file_path": file_path}

Query Parameters

• GET parameters

  • To make it Required, just remove the default value

  @app.get("/items/")
  async def read_item(skip: int, limit: int=10):
      return {'skip': skip, 'limit': limit}
  

• Optional parameters

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

• Allow for multiple path parameters and query parameters at the same time. No nee

Validations

Warning

Notice It is not Optional make FastAPI know the value is optional; The default value = None made it happened.

• Optional

  from typing import Optional
  
  @app.get('/items/')
  def get_items(q: Optional[str] = None):
      # ...
  

• Query: provide additional validations for the query parameter

  • e.g. Limit the character length

  from fastapi import Query
  
  @app.get('/optional/')
      def A(q: Optional[str] = Query(None, max_length=50)):
          # ...
  
  @app.get('/required/')
      def B(q: Optional[str] = Query(..., max_length=50)):
          # ...
  

  • parameters:
    • min_length
    • max_length
    • regex

List / multiple values

You can declare the parameter as a list to receive multiple values.

@app.get("/items/")
async def read_items(q: Optional[List[str]] = Query(None)):
    query_items = {"q": q}
    return query_items

THe URL looks like

http://localhost:8000/items/?q=foo&q=bar

And the value of q is

['foo', 'bar']

Request Body

Use Pydantic to delare the request body.

Advantages:

• Read the request body as JSON
• Convert the corresponding type
• Validate the data
• Gernerate JSON Schema for the model
• Editor support

from pydantic import BaseModel

class Item(BaseModel):
    name: str
    description: Optional[str] = None
    price: float
    tax: Optional[float] = None

@app.post("/items/")
async def create_item(item: Item):
    return item

Not using Pydantic model

Warning

Must use with other model.

class User(BaseModel):
    username: str
    full_name: Optional[str] = None

@app.post('/')
async def index(user: User, a: int = Body(...)):
    return {'a': a, **user.dict()}

Form

Warning

Install python-multipart first. pip install python-multipart

from fastapi import Form

@app.post('/')
async def index(user: str=Form(...), passwd: str=Form(...)):
    return {'user': user, 'passwd': passwd}

Info

Data form 通常是 encode 成 application/x-www-form-urlencoded，但如果有要傳檔案的話，就會 encode 成 multipart/form-data 詳見: https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods/POST

Danger

Form() 和 Body() 混用可能導致非預期結果: 因為 HTML form 是用 application/x-www-form-urlencoded 並非 application/json 所以試圖用 Body() 來拿 JSON 是錯的

TODO

Cookie

• Cookie parameter

from fastapi import Cookie

@app.get('/needCookie')
def need_cookie_route(test: Optional[str] = Cookie(...)):
    return test

• Set cookie

from fastapi import Response

@app.get('/cookie')
def set_cookie(response: Response):
    response.set_cookie(key='test', value='fuck you')
    return {'message': 'success'}

https://fastapi.tiangolo.com/advanced/response-cookies/ https://fastapi.tiangolo.com/tutorial/cookie-params/

Template

Need to install jinja2

from starlette.templating import Jinja2Templates

templates = Jinja2Templates(directory='templates')

@app.get('/')
async def main(request: Request):
    return template.TemplateResponse('index.html', {'request': request})

Endpoints

Http

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

Use starlette.endpoints.HTTPEndpoint

from starlette.endpoints import HTTPEndpoint
from starlette.responses import HTMLResponse

@app.route('/<route>/{arg}')
class Homepage(HTTPEndpoint):
    async def get(self, request):
        path_params = request.path_params
        query_params = request.query_params
        return HTMLResponse(html)

Websocket

• Controller of a websocket route
  • Send
    • .send_text()
    • .send_bytes()
    • .send_json()

@app.websocket("/ws")
async def websocket_endpoint(websocket: WebSocket):
    await websocket.accept()
    while True:
        try:
            s = await websocket.receive_text()
            await websocket.send_text(s)
        except Exception as e:
            print('error:', e)
            break

Use starlette.endpoints.WebSocketEndpoint

from starlette.endpoints import WebSocketEndpoint

@app.websocket_route("/ws")
class Endpoint(WebSocketEndpoint):
    encoding = 'text'

    async def on_connect(self, websocket):
        await websocket.accept()

    async def on_receive(self, websocket, data):
        await websocket.send_text(f'Message text was: {data}')

    async def on_disconnect(self, websocket, close_code):
        pass