I’m trying to stream a response to the client with the progress percentage after processing each file in the below code, however I see the error I/O operation on closed file for each of the files.

The response received from server:

data: {"progress": 0}

data: {"error": "Error processing file: I/O operation on closed file."}

data: {"error": "Error processing file: I/O operation on closed file."}

data: {"progress": 100}

My example

@app.post("/test-streaming")
async def upload_file_streaming(files: list[UploadFile]):
    return StreamingResponse(
        stream_response(files),
        media_type="text/event-stream"
    )



async def extract(files) -> AsyncGenerator[str, None]:
    total_files = len(files)
    for index, file in enumerate(files):
        try:
            with pdfplumber.open(file.file) as pdf:
                # Simulate processing each page of the PDF
                for page in pdf.pages:
                    text = page.extract_text()  # Replace with actual processing logic
                    await asyncio.sleep(0.5)  # Simulate processing delay

             # Calculate and yield progress
            progress = int(((index + 1) / total_files) * 100)

            yield f"data: {{"progress": {progress}}}nn"

        except Exception as e:
            yield f"data: {{"error": "Error processing file: {str(e)}"}}nn"
            


async def stream_response(files: list[UploadFile]) -> AsyncGenerator[str, None]:
    yield "data: {"progress": 0}nn"  # Initial progress
    async for update in extract(files):
        yield update
    yield "data: {"progress": 100}nn" 

I even tried reading the full file in memory by doing the below, however I see the same error

pdf_bytes = await file.read()
with pdfplumber.open(io.BytesIO(pdf_bytes)) as pdf:..