Split functionality into modules

[daniel-j-h]

Currently you have all the "business logic" in the pegasus.py file. What you normally do is split logical parts into their own modules. For example views.py module for all of your views (functions that run on a specific route endpoint) and an errorhandlers.py module for custom error handlers. You then hoist your app in the __init__.py file, import both modules and register them with your Flask app like this:

routes = [
    ('/', views.index, ['GET', 'POST']),
    ...]

for rule, view, methods in routes:
    app.add_url_rule(rule, view_func=view, methods=methods)

handlers = [
    (400, errorhandlers.bad_request),
    (401, errorhandlers.unauthorized),
    (404, errorhandlers.page_not_found),
    (403, errorhandlers.page_forbidden),
    (410, errorhandlers.page_gone),
    (500, errorhandlers.not_found),
]

for errno, handler in handlers:
    app.register_error_handler(errno, handler)

The logical structure can be something similar to: views.py for all of your view functions, models.py for classes that abstract away entities and how you store and query them in your database, and then other modules as needs be, e.g. a decorators.py with helpers such as http://flask.pocoo.org/docs/0.10/patterns/viewdecorators/#templating-decorator (good time to learn about decorators!).

Your view.py then could look similar to this:

@templated('index.html')
def index():
    return dict(userName='someUser')

[mariamrf]

I split the functionality into modules, but what I don't understand is the part where I have to register them with the Flask app? They import app from pegasus and __init__.py imports all modules after it initializes app, and it works, then what? Why do I need to register them like this also?

[daniel-j-h]

If you keep the route decorators on the view functions, you don't have to register them (again). @app.route('/') for example is fine.

Often times you want to separate the view functions (what they do, how they are implemented) and their route (is it /register or /reg or something different). If you want to do this, the common way to "link" view functions with their route by manually registering them in one place instead of using route decorators.

If you want to stay with the route decorator that's fine 👍 I just wanted to bring this to your attention.

[mariamrf]

Oh okay. That makes sense. Thank you!

[daniel-j-h]

Just today I added a little Flask server to my project and this is a perfect example of a situation where you can not use @app.route:

https://github.com/daniel-j-h/classyshoes/blob/eb717cec1ec35c54d0fa6f668005331210bd20a2/classyshoes/httpd.py

See how the Flask app (here named httpd) is only created locally in a function, so it can not be used as a decorator for the index function.

Just noted that while implementing it and thought you may be interested :)

[mariamrf]

That's an interesting take on it. Thank you for explaining! 😄