FastAPI file upload [duplicate]

Question

I am trying to upload JSON data + file (binary) to FastAPI 'POST' endpoint using requests.

This is the server code:

@app.post("/files/")
async def create_file(
    file: bytes = File(...), fileb: UploadFile = File(...), timestamp: str = Form(...)
):
    return {
        "file_size": len(file),
        "timestamp": timestamp,
        "fileb_content_type": fileb.content_type,
    }

This is the client code:

session = requests.Session()
adapter = requests.adapters.HTTPAdapter(max_retries=0)
session.mount('http://', adapter)

jpg_image = open(IMG_PATH, 'rb').read()

timestamp_str = datetime.datetime.now().isoformat()
files = {
    'timestamp': (None, timestamp_str),
    'file': ('image.jpg', jpg_image),
}
request = requests.Request('POST',
                           FILE_UPLOAD_ENDPOINT,
                           files=files)
prepared_request = request.prepare()
response = session.send(prepared_request)

The server fails with

"POST /files/ HTTP/1.1" 422 Unprocessable Entity

Please add the 422 response's body in your question for clarity. — John Moutafis
– John Moutafis, Commented Jan 14, 2021 at 10:19
For what it's worth , the response with status 422 comes from fastapi.exception_handlers.request_validation_exception_handler(req, exc) , if you are on development stage , you can set breakpoint then get more detail about the error from exc (the exception object) , the exception should describe that there is a missing field fileb , which means in your client code you should also specify the same field name fileb in the request body — T.H.
– T.H., Commented Jun 20, 2021 at 5:13
If you are trying to upload both JSON data and file(s), as mentioned in the question, please have a look at this answer as well — Chris
– Chris, Commented Jun 23, 2023 at 4:45

John Moutafis · Accepted Answer · 2021-01-14 10:18:23Z

7

FastAPI endpoints usually respond 422 when the request body is missing a required field, or there are non-expected fields, etc.

It seems that you are missing the fileb from your request body.

If this field is optional, you must declare it as follows in the endpoint definition:
```
fileb: Optional[UploadFile] = File(None)
```
You will also need to make some checks inside your endpoint code...
If it is a required field then you need to add it to your request body.

answered Jan 14, 2021 at 10:18

John Moutafis

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1 Comment

Alex Gill Over a year ago

Thanks @JohnMoutafis for the response. I fixed the endpoint to match the request and it worked. The correct code is: @app.post("/files/", status_code=201) async def create_file( file: bytes = File(...), timestamp: str = Form(...), ):

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