# Handling Forms with webapp - Google App Engine - Google Code

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# Handling Forms with webapp

If we want users to be able to post their own greetings, we need a way to process information submitted by the user with a web form. The `webapp` framework makes processing form data easy.

## Handling Web Forms With webapp

Replace the contents of `helloworld/helloworld.py` with the following:

    import cgi

    from google.appengine.api import users
    from google.appengine.ext import webapp
    from google.appengine.ext.webapp.util import run_wsgi_app

    class MainPage(webapp.RequestHandler):
        def get(self):
            self.response.out.write("""
              <html>
                <body>
                  <form action="/sign" method="post">
                    <div><textarea name="content" rows="3" cols="60"></textarea></div>
                    <div><input type="submit" value="Sign Guestbook"></div>
                  </form>
                </body>
              </html>""")

    class Guestbook(webapp.RequestHandler):
        def post(self):
            self.response.out.write('<html><body>You wrote:<pre>')
            self.response.out.write(cgi.escape(self.request.get('content')))
            self.response.out.write('</pre></body></html>')

    application = webapp.WSGIApplication(
                                         [('/', MainPage),
                                          ('/sign', Guestbook)],
                                         debug=True)

    def main():
        run_wsgi_app(application)

    if __name__ == "__main__":
        main()

Reload the page to see the form, then try submitting a message.

This version has two handlers: `MainPage`, mapped to the URL `/`, displays a web form. `Guestbook`, mapped to the URL `/sign`, displays the data submitted by the web form.

The `Guestbook` handler has a `post()` method instead of a `get()` method. This is because the form displayed by `MainPage` uses the HTTP POST method (`method="post"`) to submit the form data. If for some reason you need a single handler to handle both GET and POST actions to the same URL, you can define a method for each action in the same class.

The code for the `post()` method gets the form data from `self.request`. Before displaying it back to the user, it uses `cgi.escape()` to escape HTML special characters to their character entity equivalents. `cgi` is a module in the standard Python library; see the documentation for `cgi` for more information.

Note: The App Engine environment includes the entire Python 2.5 standard library. However, not all actions are allowed. App Engine applications run in a restricted environment that allows App Engine to scale them safely. For example, low-level calls to the operating system, networking operations, and some filesystem operations are not allowed, and will raise an error when attempted. For more information, see The Python Runtime Environment.

## Next...

Now that we can collect information from the user, we need a place to put it and a way to get it back.

Continue to Using the Datastore.