How do I pass url parameter to form value?

The form has this hidden field

<input type="hidden" name="dir_type" value="tshirt">

url parameters are

/dir?type=tshirt
/dir?type=books
/dir?type=posters

and so on.

Now I hard coded value="tshirts" but how do I get parameter for the relevant page?

I found several pages like this dealing with similar topics but I did not understand how this is done.

Thanks for y开发者_StackOverflow社区our help.

UPDATE

The answer by systempuntoout works perfectly but I decided to solve the problem without using templates. And for anyone who has a similar question, passing the url parameter to the form like this works well:

<form name="submit_form" action="/directorysubmithandler" method="post" onSubmit="return validate_form()">
title: <input type="text" name="title" size=50><br />
url: <input type="text" name="url" size=50><br />
<input type="hidden" name="dir_type" value="%s")>
<input type="submit" value="submit">
</form>""" % self.request.get("type"))                      

a. pass the type value to the view:

class Directory(webapp.RequestHandler):
    def get(self):
       ....
       merchandise_type = self.request.get("type", "")
       items = Item.all()
       items.filter("type =", merchandise_type)
       path = os.path.join(os.path.dirname(__file__), 'dir_details.html')
       self.response.out.write(template.render(path,{'type':merchandise_type}))

b. add the type value to the hidden field:

<input type="hidden" name="dir_type" value="{{ type }}">

c. get the dir_type value in your post handler:

class DirectorySubmitHandler(webapp.RequestHandler):
    def post(self):
        user = users.get_current_user()
        merchandise_type = self.request.get("dir_type", "")
        dir_type = merchandise_type
        if user:
            item = Item()
            item.title = self.request.get("title")
            item.url = self.request.get("url")
            item.type = self.request.get("dir_type")
            item.user_who_liked_this_item = user
            item.put()
            self.redirect("/dir?type=%s" %
self.request.get("dir_type"))
        else:
            self.redirect(users.create_login_url(self.request.uri))