send a file on request

app/routes.py

@@ -1,4 +1,4 @@
-from flask import render_template, flash, redirect, url_for, request
+from flask import render_template, flash, redirect, url_for, request, send_from_directory
 from app import app
 from app.forms import DownloadForm
 from datetime import datetime, timedelta
@@ -12,10 +12,12 @@ def index():
 def download():
     form = DownloadForm()
     if form.validate_on_submit():
-        flash('Download requested: {}, length={}'.format(
-            form.date.data, form.length.data))
-        return redirect(url_for('index'))
+        return render_template('download_thanks.html', title='Download', form=form)
     elif request.method == 'GET':
         form.date.data = datetime.now() - timedelta(hours = 1)
         form.length.data = 60
     return render_template('download.html', title='Download', form=form)
+
+@app.route('/download_file/<path:filename>')
+def download_file(filename):
+    return send_from_directory(app.config['DATA_DIR'], filename, as_attachment=True)

app/templates/download_thanks.html

@@ -0,0 +1,10 @@
+{% extends "base.html" %}
+
+{% block head %}
+  {{ super() }}
+  <meta http-equiv="refresh" content="0;URL='download_file/test.mp3'" />
+{% endblock %}
+
+{% block app_content %}
+    <h1>Thanks!</h1>
+{% endblock %}