How to create download API to download files using python flask

Question

I have a python code which gives a download url of an image file from azure blob storage. If we copy paste this url in browser, it simply downloads the file. I have to create a download api which when called will simply download the file. Below is the code I have as of now:

from urllib.request import urlopen
from flask import Flask, jsonify
import uuid
from flask_cors import CORS
from datetime import datetime
from azure.storage.blob import generate_blob_sas, AccountSasPermissions
import datetime
from datetime import timedelta


app = Flask(__name__)
CORS(app)

uid_secret_key = str(uuid.uuid4())

app.secret_key = uid_secret_key

# Make the WSGI interface available at the top level so wfastcgi can get it.
wsgi_app = app.wsgi_app


@app.route('/download')
def download():
    account_name = "deeusblobstorage"
    container_name = "rperodct"
    blob_name = "face_1_7285.jpg"
    account_key = "hMlIRXCjAomfDRfied8Y5FPwTVnWEkEDuVsw//CQtkiOdcFD/y5wUcxH9Ou7Ni+DtDQFwe23YbZ3Qia9gw=="
    url = f"https://{account_name}.blob.core.windows.net/{container_name}/{blob_name}"
    sas_token = generate_blob_sas(
        account_name=account_name,
        account_key=account_key,
        container_name=container_name,
        blob_name=blob_name,
        permission=AccountSasPermissions(read=True),
        expiry=datetime.datetime.utcnow() + timedelta(hours=1)
    )

    url_with_sas = f"{url}?{sas_token}"
    print(url_with_sas)
    urlopen(url_with_sas)


@app.route('/')
def hello_world():
    return jsonify({'Status': 'ok', 'date': '05.25.21'}), 200


if __name__ == '__main__':
    import os

    HOST = os.environ.get('SERVER_HOST', 'localhost')
    try:
        PORT = int(os.environ.get('SERVER_PORT', '5555'))
    except ValueError:
        PORT = 5555
    app.run(HOST, PORT)

/download api contains the code which gets the download url of a blob from azure container in variable name url_with_sas . Now I want to make this API in such a way that if we hit this, it should automatically download the file from the url. So for this I thought of adding urlopen(url_with_sas) which will open the url. But seems like its not working. Can anyone give some suggestions for this. Thanks

Answer 1

As in the comment mentioned the solution is via a return redirect(url_with_sas) so the whole function looks like this:

@app.route('/download')
def download():
    account_name = "deeusblobstorage"
    container_name = "rperodct"
    blob_name = "face_1_7285.jpg"
    account_key = "hMlIRXCjAomfDRfied8Y5FPwTVnWEkEDuVsw//CQtkiOdcFD/y5wUcxH9Ou7Ni+DtDQFwe23YbZ3Qia9gw=="
    url = f"https://{account_name}.blob.core.windows.net/{container_name}/{blob_name}"
    sas_token = generate_blob_sas(
        account_name=account_name,
        account_key=account_key,
        container_name=container_name,
        blob_name=blob_name,
        permission=AccountSasPermissions(read=True),
        expiry=datetime.datetime.utcnow() + timedelta(hours=1)
    )

    url_with_sas = f"{url}?{sas_token}"
    return redirect(url_with_sas)