Lecture 5

In this class, we started web2py.

Documentation

The documentation for web2py can be found in the web2py book; over the next week, we will go over the overview.

Code

The code developed in class was posted in the oct-8-2018 branch of the web2py start app.

To get this code, proceed as follows:

Install the source package of web2py if you haven't done it already.

You should have, as a result, a web2py directory, with a file web2py.py into it.

Proceed as follows.

Go into the applications directory:

cd applications

Get the code repository, into a directory called start:

git clone https://luca_de_alfaro@bitbucket.org/luca_de_alfaro/web2py_start.git start

Check out the oct-8-2018 branch:

cd start

git checkout oct-8-2018

To run the code, just go to the top-level directory, the one where web2py.py is, and do:

python web2py.py -e

The final -e means, please log all the errors to the console.

Summary

As a summary, in class we learned the main control flow with which web2py answers a web request.

This flow is documented in the web2py book, chapter core, but here it is summarized:

• When the request is serviced, the first thing that runs are the models, in the models directory, in alphabetical order.
  • The first model is db.py. This model defines the following very important things:
    • The db object, which is used to talk to the database.
    • The auth object, which is used for user authentication, and which we will use to figure out whether the user is logged in, what's the user email, etc.
    • The session object, which is used to store data related to the user session.
  • The second model is menu.py. This model just defines the menu in the top bar of the site.
  • The third model is tables.py; for now it's empty, but we will put there the definitions of our database tables.
• Once the models run, the controller is run. A request to http://mysite/myapp/mycontroller/myfunc is serviced by the function myfunc, defined in the controller mycontroller.py of the application myapp.
• The controller produces as output a dictionary (it can produce also other things, such as a file download, but we will deal with that later).
• The dictionary is passed to a view, in views/mycontroller/myfunc.html . The view is a template, which is filled in with the information in the dictionary, creating an HTML page that is then sent back to the user.