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
webapp2
framework makes processing form data easy.
From Hello World to Guestbook
In order to prepare the Hello World app we've created thus far, please make the following changes:
-
Rename the top level
helloworld
directory toguestbook
-
Rename
helloworld.py
toguestbook.py
-
Replace the
handlers
section ofapp.yaml
with:
Restart the development server using the new
guestbook
directory.
Handling Web Forms With webapp2
Declare that you are using
webapp2
by adding this
libraries
section to your
app.yaml
:
Replace the contents of
guestbook/guestbook.py
with the following:
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.