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What are query parameters?

In FastApi, when you declare other function parameters that are not path parameters, they are automatically interpreted as “query string” parameters.

The sample code

from fastapi import FastAPI
import uvicorn

app = FastAPI()
goods=['xiaomi'.'apple'.'huawei'.'oppo']

@app.get('/goods/')
async def get_goods(start:int = 0,end:int = 3) :
    return goods[start:end]

if __name__ == "__main__":

    uvicorn.run(app='main:app',host='0.0.0.0',reload=True,debug=True)
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The interface test

With parameters

Band partial parameter

Since both query parameters have default values in the view function behind the scenes, we can test the request by modifying individual parameters.

Use default parameters

When we send a request without query parameters, the background will use the default parameters to process the request after receiving it. Start =1, end=3

Optional parameters

In our actual development, some parameters may or may not be required, depending on the needs of users.

The sample code

@app.get('/name/{name}/age/{age}')
async def get_userinfo(name:str,age:int,j:Optional[bool] =False) :
    ret = {'Name':name}
    if j:
        ret.update({'Age':age})
    return ret
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Age is not returned by default. When j is true, age information is returned.

The interface test

A normal request that does not return age information by default

A request with parameter j returns age information

Parameter type conversion

As mentioned above, when we carry the parameter j for the request, its value is True. FastApi provides us with a more convenient way to query the parameter type conversion, that is, when its value is any True value, the request processing can be completed.

The sample request

Request operation at j=1

Request operation at j=0

This parameter is mandatory

In real development, we might need the user to carry a parameter to complete the request.

code

All we need to do is add a parameter q to the code above and FastApi will do the rest for us.

@app.get('/name/{name}/age/{age}')
async def get_userinfo(name:str,age:int,q:bool,j:Optional[bool] =False) :
    ret = {'Name':name}
    if j:
        ret.update({'Age':age})
    return ret
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The interface test

When a request is made without q

Prompt Query parametersqmissing

Request with q parameter

The request is successful

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