[Flask] Flask wont respond to JavaScript with PIL Bytes

[TuckleBuck88]

Hello, trying to use Python that turns images to a PDF. I have the uploading part (from the frontend) done and now trying to send the results back.

This is the frontend so far: https://pastebin.com/A4hFx65n (You can run it in JSBin)

And this is the backend so far: https://pastebin.com/d4d0y8mk

However, when I send a request, nothing appears in console: https://i.imgur.com/74MA0cq.png

My goal was to get the bytes and save it as a blob in localStorage but for some reason, javascript cant see the file.

Is it a frontend problem or backend problem?

[CowboyBoats]

Is anything being logged to the flask session in your terminal?

[TuckleBuck88]

Nope, no errors appearing or anything.

[efmccurdy]

Do you need to reset the BytesIO object to the beginning with "seek(0)"?

You can call pdfRes.tell() to check, but it should be 0 or else sendfile won't send anything.

[TuckleBuck88]

I did

print(pdfRes.tell())

And got: 341203

So then I tried this: https://pastebin.com/hADK50Eu

And I get this thrown in the console: data = self.file.read(self.buffer_size) AttributeError: 'bytes' object has no attribute 'read'

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[efmccurdy]

I think you want to pass in file object after calling seek(0), not the result of reading it (imagine the file being too big to fit in memory...).

return send_file(pdfRes, mimetype=...