File extension validation

Is there a way to validate the file format of an input file as a request? If the fastapi app will only accept incoming requests with files that have extensions .pdf,.docx or .txt, how will I implement this using fastapi? Something similar is used in the laravel framework https://stackoverflow.com/questions/32179164/how-to-validate-a-file-type-in-laravel

Example

from fastapi import FastAPI

app = FastAPI()


@app.post("/upload")
def read_file(input_file: UploadFile = File(..., format=[".txt",".pdf",".docx"])):
    return {"filename": "input_file.filename"}

[frankie567]

You can check the MIME type, which should be more accurate than the file extension (https://fastapi.tiangolo.com/tutorial/request-files/#uploadfile). Example:

@app.post("/upload")
def read_file(input_file: UploadFile = File(...)):
    if input_file.content_type not in ["application/pdf", "text/plain", "application/vnd.openxmlformats-officedocument.wordprocessingml.document"]:
        raise HTTPException(400, detail="Invalid document type")
    return {"filename": "input_file.filename"}

Of course, you can wrap this logic in a dependency to reuse it in several endpoints.

[frankie567]

Actually, you need to set the content type of the file, not the whole request.

The file tuple parameter can accept a third value which is the content type of the file: https://requests.readthedocs.io/en/latest/user/advanced/#post-multiple-multipart-encoded-files