title: Python Flask request.form not working
body: <p>I have a question about Python.
  I am trying to get multiple buttons in one form, but it isn't working out.</p>
  
  <p>I have tried using <code>if 'elem' in request.form</code>, but that isn't working, because the submit's doesn't go in <code>request.form</code>. You have any idea how it comes?</p>
  
  <p>I have already tried solving it with this: <a href="https://stackoverflow.com/questions/19794695/flask-python-buttons">Flask Python Buttons</a>
  But that didn't work out.
  Google isn't working for me aswell, hence why trying it on here.</p>
  
  <p>Python code:</p>
  
  <pre><code>@app.route('/option_new_sender/', methods = ['GET','POST'])
  def option_new_sender():
  # Add selected elements to session['added_elements']
  if 'add_elem' in request.form:
      return 'a'
  # Delete Selected elements from session['added_elems']
  elif 'remove_elem' in request.form:
      return 'b'
  # Reset verwijderd session['added_elems']
  elif 'reset' in request.form:
      return 'c'
  # Verzend form en voegt toe aan 'entries_plot_list
  elif 'send_form' in request.form:
      return 'd'
  else:
      return 'e'
  </code></pre>
  
  <p>HTML code:</p>
  
  <pre><code>&lt;form action={{url_for("option_new_sender")}} method="POST"&gt;
  &lt;h2&gt;Een nieuwe grafiek toevoegen&lt;/h2&gt;
  Titel: &lt;input type="text" name="title" value={{title}}&gt;&lt;br/&gt;
  Perc: &lt;input type="text" name="perc" value={{perc}}&gt;&lt;br/&gt;
  &lt;select name = "added_elems" multiple size="5"&gt;
      {% for elem in elems %}
          &lt;option value = "{{elem}}"&gt;{{elem}}&lt;/option&gt;
      {% endfor %}
  &lt;/select&gt;
  &lt;button type= "submit" value = "remove_elem"&gt;Remove element&lt;/button&gt;
  &lt;/br&gt;&lt;/br&gt;
  Element: 
  &lt;select name = "elem" multiple size = "5"&gt;
      {% for elem in all_elems %} 
          &lt;option value = "{{elem}}"&gt;{{elem}}&lt;/option&gt;
      {% endfor %}
  &lt;/select&gt;
  &lt;button type="submit" value = "add_elem"&gt;Add element&lt;/button&gt;
  &lt;button type="submit" value = "send_form"&gt;Verzenden&lt;/button&gt;
  &lt;button type="submit" value = "reset"&gt;Reset&lt;/button&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>It doesn't matter what I try, for some reason the Submit always ends at 'e'.
  Thank you in advance!</p>