How to make the argument to filter() a variable?

I have this model

class Item(db.Model):
    ...   
    glam = db.StringProperty()
    casual = db.StringProperty()
    speaking = db.StringProperty()

and this handler with开发者_如何学C a form with radio buttons:

class SortForm(webapp.RequestHandler):
    def get(self):
        self.response.out.write("""
            <form name="submit_form" action="/sortformhandler" method="post">
            Category: <input type="radio" name="image" value="image"> Image <br />
            Sorty by tag: <br />
            <input type="radio" name="tag" value="glam" /> Glam <br />
            <input type="radio" name="tag" value="formal" /> Formal <br />
            <input type="radio" name="tag" value="speaking" /> Speaking <br />
            <input type="submit" value="submit">
            </form>
            """)

and this handler

class SortFormHandler(webapp.RequestHandler):
    def post(self):

        query = Item.all()

        query.filter("glam =", "glam")
                for item in query:
            self.response.out.write("""<a href="%s"><image src="%s" height="110">%s</a>""" % 
                                       (item.url, item.image_source_url, item.title)  )

I've been trying to have something like

        query.filter("[self.request.get("tag")] =", [self.request.get("tag")])

so that when glam is chosen in the radio button I should have

        query.filter("glam =", "glam")

But I could not make this work. In other words, I am trying to make the argument to filter() a variable. Any suggestions?

I am trying to create tagging for the image library. Thanks.

Would that do what you're looking for:

choice = self.request.get("tag")
query.filter(choice, choice)

However, I agree with Wooble below. The way you have designed it, you dont' really use glam, casual, speaking as StringProperty, since they are either empty or have a specific value.

What you probably want to do is have a tag property that can take different values from glam, formal, speaking, ...

class Item(db.Model):
    ...   
    tag = db.StringProperty()

And then you would query your db like so:

query.filter("tag", self.request.get("tag"))

query.filter(self.request.get("tag"), self.request.get("tag"))

The = is actually not required.

However, I'd also consider using a single StringProperty for the tag, since it appears that your 3 string properties are essentially booleans, and only one of them can be true at a time.