This is my implementation of a Masterpage like solution in Python. When using django.utils.simplejson it is possible to render Html Template against your Phython data.
First of all we can fetch the Url in a variable and map it to an Html Template file. A call template_values['content'] = template.render(content,template_values) will render the template and stores the result in a Data Array.
After that we can render the index.html (Our Python MasterPage File) and pass the requested template to the MainPage rendering process.

class MainPage(webapp.RequestHandler):
	def post(self):
		get()
	def get(self):
		data_query = MyData.all().order('-date')
		data = data_query.fetch(10)
		master = os.path.join(os.path.dirname(__file__), 'index.html')
		u = (string.split(self.request.url,"/")[3])
		content = os.path.join(os.path.dirname(__file__), '_'+u+'.html')
		template_values = {}
		#if u <> "":
		template_values = {
			"content": "",
			"data1": "x",
			"data2": "y"
		}
		template_values['content'] = template.render(content,template_values)
		self.response.out.write(template.render(master, template_values))