Write CSV files to a Zip file and serve with Falcon (Python)

app.py

import csv
import io
import tempfile
import zipfile

import falcon

GB = 1024 ^ 3
MEM_MAX_SIZE = 1 * GB


def add_csv(zf, fname, rows):
    csv_fo = tempfile.SpooledTemporaryFile(max_size=MEM_MAX_SIZE, mode='w', encoding='utf-8')

    cw = csv.writer(csv_fo)
    for r in rows:
        cw.writerow(r)

    csv_fo.seek(0)
    zf.writestr(fname, csv_fo.read())


def create_zip():
    zip_fo = tempfile.SpooledTemporaryFile(max_size=MEM_MAX_SIZE, mode='w+b')
    with zipfile.ZipFile(zip_fo, 'w', compression=zipfile.ZIP_DEFLATED) as zf:
        add_csv(zf, 'letters.csv', (
            ('a', 'b', 'c'),
            ('d', 'e', 'f'),
        ))

        add_csv(zf, 'numbers.csv', (
            ('1', '2', '3'),
            ('4', '5', '6'),
        ))
    zip_fo.seek(0)
    return zip_fo


class Index:
    def on_get(self, req, resp):
        resp.content_type = falcon.MEDIA_HTML  # Default is JSON, so override
        resp.text = 'Hello World!'
        resp.text += '<a href="/csv">example csv</a>'


class CSV:
    def on_get(self, req, resp):
        resp.content_type = 'application/zip'
        resp.set_header('Content-Disposition', 'attachment; filename=data.zip')
        resp.stream = create_zip()


# falcon.App instances are callable WSGI apps
# in larger applications the app is created in a separate file
app = application = falcon.App()

app.add_route('/', Index())
app.add_route('/csv', CSV())

Can be ran with: $ gunicorn --reload app