Google App Engine with Python does not provide built in session capabilities. This step by step walkthrough sets up a Google App Engine app using the lightweight gae-sessions utility.
1. Download gae-sessions
Download the gae-sessions code from https://github.com/dound/gae-sessions/
2. Create your app directory
Create a directory for your application. I’ll be using gaesessiontest/
3. Copy gaesessions to your app
From the gae-sessions download file, copy the gaesessions/ directory to your app directory.
4. Create your app.yaml file
Within your app directory create an app.yaml file with the contents:
application: gaesessiontest version: 1 runtime: python api_version: 1 handlers: - url: /.* script: main.py
5. Create your appengine_config.py file
Within your app directory create an appengine_config.py file with the contents:
from gaesessions import SessionMiddleware def webapp_add_wsgi_middleware(app): app = SessionMiddleware(app, cookie_key="You must change this") return app
6. Change the cookie_key
Change the cookie_key value to a secret combination of characters.
7. Create your main.py file
Within your app directory create a main.py file with the contents:
import os from google.appengine.ext import webapp from google.appengine.ext.webapp.util import run_wsgi_app from google.appengine.ext.webapp import template from gaesessions import get_current_session class MainPage(webapp.RequestHandler): def get(self): # Get the current session session = get_current_session() # Get the value of the counter, # defaulting to 0 if not present counter = session.get('counter', 0) # Increment the counter session['counter'] = counter + 1 context = { "counter": counter } path = os.path.join(os.path.dirname(__file__), 'index.html') self.response.out.write(template.render(path, context)) application = webapp.WSGIApplication( [('/', MainPage)], debug=True) def main(): run_wsgi_app(application) if __name__ == "__main__": main()
8. Create your index.html file
Within your app directory create an index.html file with the contents:
<!DOCTYPE html> <html lang="en"> <head> <title>GAE Sessions</title> </head> <body> Counter = {{ counter}} </body> </html>
9. Run your application
My GAE installation is located in /opt/google_appengine/ so I start the application with the command:
/opt/google_appengine/dev_appserver.py gaesessiontest
10. View your app
Open your browser and go to http://localhost:8080/. You should see a counter that increments each time you refresh the page.
3 Comments
On the line where you increment the counter:
session['counter'] = session['counter'] + 1
the 2nd “session['counter']” should be replaced by “counter” like this:
session['counter'] = counter + 1
because you’re retrieving a value that does not exist yet (on the first visit) and this will generate a KeyError.
Thanks for the post btw. Nice to-the-point example.
Works like a charm!
@Jeroen, thanks for the fix – post updated.
One Trackback
[...] This post was mentioned on Twitter by cfbloggers. cfbloggers said: How to use sessions on Google App Engine with Python and gae-sessions? – http://cfbloggers.org/?c=46806 [...]