Headers and Query Parameters in FastAPI

FastAPI is a modern web framework for building APIs with Python. It provides a simple and intuitive way to work with headers and query parameters in your API endpoints. Headers are used to pass additional information in the request, while query parameters are used to filter or paginate the response.

Headers

Headers in FastAPI can be accessed using the request object. You can specify required headers and their types using dependencies. For example:

from fastapi import FastAPI, Header

app = FastAPI()

@app.get("/")
async def read_item(user_agent: str = Header(None)):
    return {"User-Agent": user_agent}

In this example, we are specifying a required header ‘User-Agent’ and retrieving its value in the ‘/items’ endpoint. If the header is not provided in the request, FastAPI will return a 422 response with an error message.

Query Parameters

Query parameters can be accessed in FastAPI using the query string. You can specify query parameters and their types using the request object. For example:

from fastapi import FastAPI

app = FastAPI()

@app.get("/")
async def read_item(skip: int = 0, limit: int = 10):
    return {"skip": skip, "limit": limit}

In this example, we are specifying two query parameters ‘skip’ and ‘limit’ in the ‘/items’ endpoint. The default values for these parameters are 0 and 10 respectively. You can pass values for these parameters in the request URL like ‘/items?skip=5&limit=20’.

Conclusion

Headers and query parameters are important features in FastAPI to customize your API requests and responses. By using these features, you can make your API more flexible and interactive. FastAPI provides a simple and easy way to work with headers and query parameters, making it a great choice for building APIs in Python.