Migrating to Python 2.7, part 2: Webapp and templates

In part 1 of the migration series, we discussed changes to your app to take advantage of the 2.7 runtime's support for multithreading. Today, we'll start looking at the changes to the included libraries, and how we'll have to modify our app to use them.


First up is the replacement of App Engine's lightweight webapp framework with webapp2. Webapp2 is an external open-source project, which says it "follows the simplicity of webapp, but improves it in some ways: it adds better URI routing and exception handling, a full featured response object and a more flexible dispatching mechanism". Webapp2 does an excellent job of maintaining compatibility with webapp, which is why it was chosen as a replacement, but it also adds a number of useful improvements on it.

To see what's changed in concrete terms, let's assume we have a very straightforward app that looks something like this:

import os

from google.appengine.ext import webapp
from google.appengine.ext.webapp import template

class BaseHandler(webapp.RequestHandler):
  def render_template(self, filename, **template_args):
	path = os.path.join(os.path.dirname(__file__), 'templates', filename)
	self.response.out.write(template.render(path, template_args))

class IndexHandler(BaseHandler ...