Flask голосовалака: почему здесь ошибка? - Python

# coding: utf8
 
from flask import Flask, render_template, request
import os
app = Flask(__name__)
 
poll_data = {
   'question': 'Which web framework do you use?',
   'fields': ['Flask', 'Django', 'TurboGears', 'web2py', 'pylonsproject']
}
filename = 'data.txt'

@app.route('/')
def root():
    return render_template('flask_gol.html', data=poll_data)

@app.route('/poll')
def poll():
    vote = request.args.get('field')
 
    out = open('data.txt', 'a')
    out.write(vote + '\n')
    out.close()
 
    return render_template('thank.html', data=poll_data)

@app.route('/results')
def show_results():
    votes = {}
    for f in poll_data['fields']:
        votes[f] = 0
 
    f = open('data.txt', 'r')
    for line in f:
        vote = line.rstrip("\n")
        votes[vote] += 1
 
    return render_template('results.html', data=poll_data, votes=votes)

if __name__ == "__main__":
    app.run(debug=True)