Python – How do I implement tags in a webapp?

I’m trying to make a basic quote sharing app using Webapp. Obviously, being able to assign arbitrary labels to each reference is crucial.

Here’s the relevant code I came up with:
(Mostly from the sample chat application from the great introductory book “Using Google App Engine”).

class Quote(db. Model):
  user = db. ReferenceProperty()
  text = db. StringProperty()
  tags = db. StringListProperty()
  created = db. DateTimeProperty(auto_now=True)

and “View”:

class QuoteHandler(webapp. RequestHandler):

def get(self):
    que = db. Query(Quote).order('-created');
    chat_list = que.fetch(limit=10)
    doRender(
          self,
          'quote.htm',
          { 'quote_list': quote_list })

def post(self):
    self.session = Session()
    if not 'userkey' in self.session:
      doRender(self, 'quote.htm', {'error' : 'Must be logged in'} )
      return

msg = self.request.get('message')
    if msg == '':
      doRender(self,'quote.htm',{'error' : 'Blank quote ignored'} )
      return
    tgs = self.request.get('tags') #really not sure of this
    newq = Quote(user = self.session['userkey'], text=msg, tags= tgs)
    newq.put();
    self.get();

In quote.htm I have:

{% extends "_base.htm" %}
{% block bodycontent %}
      <h1>Quotes</h1>
      <p>
      <form method="post" action="/quote">
        Quote:<input type="text" name="message" size="60"/><br />
        Tags: <input type="text" name="tags" size="30"/>
      <input type="submit" value="Send"/> 
      </form>
      </p>
      {% ifnotequal error None %}
       <p>
       {{ error }}
       </p>
      {% endifnotequal %}
<br />
<h3> The latest quotes </h3>

{% for quote in quote_list %}
        <p>
           {{ quote.text }}<br />
         ({{quote.user.account}}) <br />
         {{ quote.tags }}

{{ quote.created|date:"D d M Y" }}
        </p>
      {% endfor %}
{% endblock %}

However, this combination is wrong. I get:

BadValueError: Property tags must be a list

Whatever I type in the tag field, and (obviously) I’m new to Python and Webapp. I googled a lot but couldn’t find any guidelines for implementing the label. So I really appreciate your help fixing this bug, or rather, I pointed out a more elegant way to handle labels.

Before creating your quote, try using split() to convert tgs to a word list. Tags should be separated by spaces in your form, otherwise you can add a parameter to split if you prefer to separate them with something else.

...
tgs = self.request.get('tags').split()
newq = Quote(user = self.session['userkey'], text=msg, tags= tgs)
...