How to pass URL as a path parameter to a FastAPI route?

I have created a simple API using FastAPI, and I am trying to pass a URL to a FastAPI route as an arbitrary path parameter.

from fastapi import FastAPI
app = FastAPI()
@app.post("/{path}")
def pred_image(path:str):
    print("path",path)
    return {'path':path}

When I test it, it doesn’t work and throws an error. I am testing it this way:

http://127.0.0.1:8000/https://raw.githubusercontent.com/ultralytics/yolov5/master/data/images/zidane.jpg

Answer

Option 1

You can simply use the path convertor to capture arbitrary paths. As per Starlette documentation, path returns the rest of the path, including any additional / characters.

from fastapi import Request

@app.get('/{_:path}')
def pred_image(request: Request):
    return {"path": request.url.path[1:]}

or

@app.get("/{full_path:path}")
def pred_image(full_path: str):
    return {"path": full_path}

Test using the below:

http://127.0.0.1:8000/https://raw.githubusercontent.com/ultralytics/yolov5/master/data/images/zidane.jpg

Output:

{"path":"https://raw.githubusercontent.com/ultralytics/yolov5/master/data/images/zidane.jpg"}

Test using HTML <form>:

If you would like to test the above by passing the URL through an HTML <form>, instead of manually typing it after the base URL, please have a look at Option 3 of this answer, which demonstrates how to convert the form <input> element into a path parameter on <form> submission.

Option 2

As @luk2302 mentioned in the comments section, your client (i.e., either end user, javascript, etc) needs to encode the URL. The encoded URL, however, as provided by @luk2302 does not seem to work, leading to a "detail": "Not Found" error. As it turns out, you would need to encode it twice to work. That is:

http://127.0.0.1:8000/https%253A%252F%252Fraw.githubusercontent.com%252Fultralytics%252Fyolov5%252Fmaster%252Fdata%252Fimages%252Fzidane.jpg

On server side, you can decode the URL (twice) as follows:

from urllib.parse import unquote 

@app.get("/{path}")
def pred_image(path: str):
    return {'path':unquote(unquote(path))}  

Option 3

Since your endpoint seems to accept POST requests, you might consider having the client sending the image URL in the body of the request, instead of passing it as a path parameter. Please have a look at the answers here, here and here, as well as FastAPI’s documentation, on how to do that.

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Note:

If you are testing this through typing the aforementioned URLs into the address bar of a browser, then keep using @app.get() routes, as when you type a URL in the address bar of your browser, it performs a GET request. If , however, you need this to work with POST requests, you will have to change the endpoint’s decorator to @app.post() (as shown in your question); otherwise, you would come accross {"detail":"Method Not Allowed"} error.