How do you return a file from an API response flask_restful?

Question

I Have two API's one is basically for generating PDF's basing on the data sent.

This first API endpoint below

http://localhost:5000/api/sendReceiptData

Returns a PDF file as an attachment.

The second API will consume the first API and should return a PDF as an attachment in the response. I have tried it out but I get this error TypeError: Object of type bytes is not JSON serializable

How can I therefore return a file response from the first API within this second API

---

EDIT: I have this same specific scenario and adding this edit since the question was marked as duplicate/closed. The link to the duplicate question shows how to serve a file that you already have stored locally. But I wanted a way to serve the file from memory as soon as it was retrieved from the first API call because I do not want the file stored on the webserver. The file in my scenario can be any format including audio, doc, pdf, image, etc. Here is how I was able to do this:

# Make GET call to API to retrieve file in response
response = requests.get(url, auth=(user, pwd), headers=headers, stream=True)
response.raw.decode_content = True

# Forward json error received from failed GET call
if response.status_code != 200:
    return {**response.json()}, response.status_code

# Forward raw file received from successful GET call 
return send_file(response.raw, attachment_filename=file_name, as_attachment=True)

Answer 1

You need to use send_file method to return pdf file

import os
from flask import Flask, make_response, send_file
from werkzeug.utils import secure_filename

app = Flask(__name__)
PDF_FOLDER = '/path/to/pdf/folder'  # Replace with the path to your PDF folder

@app.route("/pdf/<string:filename>", methods=['GET'])
def return_pdf(filename):
    try:
        filename = secure_filename(filename)  # Sanitize the filename
        file_path = os.path.join(PDF_FOLDER, filename)
        if os.path.isfile(file_path):
            return send_file(file_path, as_attachment=True)
        else:
            return make_response(f"File '{filename}' not found.", 404)
    except Exception as e:
        return make_response(f"Error: {str(e)}", 500