Python-FastAPI introductory tutorial

I. Introduction

Recently I'm doing web development, the web with front and back ends separated. The front-end framework uses Vue, the front-end component library is Element-UI, and the back-end is hovering in Django-Rest-Framework, Flask, and FastApi. Tested one by one. Finally, FastApi was chosen.

The reasons are as follows:

1. Django-Rest-Framework: It feels cumbersome, and the official documentation is not friendly enough for novices, and it is more difficult for me, a layman in web development.
2. Flask: It's relatively lightweight, but it's not very suitable for api development, and it needs specific functions for conversion.
3. FastApi: It has its own api documentation (the interface is very beautiful, and there is no need to write additional pages for testing during development), and it is very friendly to the json format api.

The following picture shows the built-in test interface:

2. Case

Hello World

The following is a case of Hello world. Create a new helloworld.pyscript.

import uvicorn
from fastapi import FastAPI

app = FastAPI()

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

uvicorn.run(app=app)

In the above script, uvicornit is a ASGIserver. The default port 8000, the default hostis localhost. It may be performed by the following methods portand hostmodifications.

Use app.get('/')registered route, when the address is accessed, the dictionary will return the corresponding ( JSONstring)

    uvicorn.run(app, host="127.0.0.1", port=8000)

Open 127.0.0.1:8000/docs to test. Test results using docs

Bringing such a document has a great advantage-it reduces the time to write a test interface. FastApi can also directly use the JSONformat return (also supports there are better ways, such as on the case below)

In this case, the advantages of docs are not reflected. Because you don't need any input, you can get the output.

input Output

from fastapi import FastAPI
from pydantic import BaseModel, EmailStr

app = FastAPI()


class UserIn(BaseModel):
    username: str
    password: str
    email: EmailStr
    full_name: str = None


class UserOut(BaseModel):
    username: str
    email: EmailStr
    full_name: str = None


@app.post("/user/", response_model=UserOut)
async def create_user(*, user: UserIn):
    return user


# pip install pydantic[email]
if __name__ == '__main__':
    import uvicorn
    uvicorn.run(app, host="127.0.0.1", port=8000)

In the function, define parameters for the user: UserInshow need to enter the data in line with UserInthe model. Configured response_modelto UserOut, indicating that the output data are consistent with UserOutthe model. FastApi will automatically filter

enter

Output

The built-in document can display all the schemas (Schemas), which will correspond to the classes in the code (you can use the dictionary to initialize quickly).

Other advantages

1. Other templates can be introduced
2. Official tutorial very friendly to novices