title: python 3 Login form on webpage with urllib and cookiejar
body: <p>I've been trying to make a python script login to my reddit account but it doesnt seem to work, could anybody tell me whats wrong with my code? It runs fine it just doesnt login.¨</p>
  
  <pre><code>cj = http.cookiejar.CookieJar()
  opener = urllib.request.build_opener(urllib.request.HTTPCookieProcessor(cj))
  opener.addheaders = [('User-agent', 'Mozilla/5.0')]
  urllib.request.install_opener(opener)
  authentication_url = 'https://ssl.reddit.com/post/login'
  payload = {
      'op': 'login',
      'user_name': 'username',
      'user_pass': 'password'
  }
  data = urllib.parse.urlencode(payload)
  binary_data = data.encode('UTF-8')
  req = urllib.request.Request(authentication_url, binary_data)
  resp = urllib.request.urlopen(req)
  contents = resp.read()
  </code></pre>