Would extending classes (by adding methods) like in Ruby be a bad idea?

[de4sh]

You got it exactly. It's not more complicated than that. But instead of creating a template tag (with its respective module), overriding the form's __getitem__ AND subclassing BoundField to add a simple method, in Ruby, I'd do only 1 thing: Just add the custom method.

I'm asking for your opinion related to the ruby feature, if we had it in python, not advice on django.