Flask button to save table from query as csv - sql

Question

I have a flask app that runs a query and returns a table. I would like to provide a button on the page so the user can export the data as a csv.
The problem is that the query is generated dynamically based on form input.
#app.route('/report/<int:account_id>', methods=['GET'])
def report(account_id):
if request == 'GET':
c = g.db.cursor()
c.execute('SELECT * FROM TABLE WHERE account_id = :account_id', account_id=account_id)
entries = [dict(title=row[0], text=row[1]) for row in c.fetchall()]
return render_template('show_results.html', entries=entries)
On the html side it's just a simple table, looping over the rows and rendering them. I'm using bootstrap for styling, and included a tablesorter jquery plugin. None of this is really consequential. I did try one javascript exporter I found, but since my content is rendered dynamically, it saves a blank CSV.
Do I need to do some ajax-style trickery to grab a csv object from the route?

Answer 1

I solved this myself. For anyone who comes across this I find it valuable for the specific use case within flask. Here's what I did.
import cx_Oracle # We are an Oracle shop, and this changes some things
import csv
import StringIO # allows you to store response object in memory instead of on disk
from flask import Flask, make_response # Necessary imports, should be obvious
#app.route('/export/<int:identifier>', methods=['GET'])
def export(load_file_id):
si = StringIO.StringIO()
cw = csv.writer(si)
c = g.db.cursor()
c.execute('SELECT * FROM TABLE WHERE column_val = :identifier', identifier=identifier)
rows = c.fetchall()
cw.writerow([i[0] for i in c.description])
cw.writerows(rows)
response = make_response(si.getvalue())
response.headers['Content-Disposition'] = 'attachment; filename=report.csv'
response.headers["Content-type"] = "text/csv"
return response

Answer 2

For anyone using flask with sqlalchemy, here's an adjustment to tadamhicks answer, also with a library update:
import csv
from io import StringIO
from flask import make_response
si = StringIO()
cw = csv.writer(si)
records = myTable.query.all() # or a filtered set, of course
# any table method that extracts an iterable will work
cw.writerows([(r.fielda, r.fieldb, r.fieldc) for r in records])
response = make_response(si.getvalue())
response.headers['Content-Disposition'] = 'attachment; filename=report.csv'
response.headers["Content-type"] = "text/csv"
return response