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Fast API 404 Not Found
Understanding FastAPI
FastAPI is a modern, fast (high-performance), web framework for building APIs with Python 3.6+ based on standard Python type hints. It is designed to be easy to use and to provide high performance, on par with NodeJS and Go. FastAPI is particularly useful for creating RESTful APIs quickly and efficiently, leveraging automatic interactive API documentation and validation.
Identifying the Symptom: 404 Not Found
One common issue developers encounter when working with FastAPI is the '404 Not Found' error. This error occurs when the server cannot find the requested resource. In the context of FastAPI, this typically means that the URL path or endpoint being accessed does not exist or is incorrectly defined.
Explaining the 404 Not Found Error
The HTTP 404 Not Found response status code indicates that the server cannot find the requested resource. Links that lead to a 404 page are often called broken or dead links and can be subject to link rot. In FastAPI, this error usually arises when the endpoint is not correctly defined or the URL path is incorrect.
Common Causes of 404 Errors in FastAPI
- Incorrect URL path: The URL path specified in the request does not match any defined routes in the FastAPI application.
- Missing endpoint: The endpoint has not been defined in the application, or there is a typo in the route definition.
- Method mismatch: The HTTP method used in the request does not match the method defined for the endpoint.
Steps to Fix the 404 Not Found Error
Verify the URL Path
Ensure that the URL path you are trying to access matches exactly with the route defined in your FastAPI application. Check for typos or missing segments in the path. For example, if your FastAPI app has a route defined as @app.get('/items/{item_id}'), ensure that your request URL matches this pattern.
Check Endpoint Definitions
Review your FastAPI application code to ensure that the endpoint is correctly defined. Make sure that the route decorator (e.g., @app.get(), @app.post()) is applied to the correct function and that the path matches the intended URL.
Ensure Correct HTTP Method
Verify that the HTTP method used in the request matches the method defined for the endpoint. For instance, if the endpoint is defined with @app.get(), ensure that the request is a GET request.
Use Interactive API Documentation
FastAPI provides automatic interactive API documentation with Swagger UI and ReDoc. You can access these by navigating to /docs or /redoc in your FastAPI application. These tools can help you verify the available endpoints and their expected parameters.
Additional Resources
For more information on FastAPI and handling common errors, consider visiting the following resources:
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