arent classes just useless? you can just use a dict or in most cases just save it in a picke...
Classes in python aren't useless. Good code is more than just getting the thing to work. Classes provide an opportunity for the programmer to define an informative and descriptive interface for the logic being encapsulated. Instance/Class methods, constructor methods, and Meta classes allow for that!
Jamming everything into a dictionary, is, as you point out, sometimes possible, but would frequently sacrifice opportunities to organize the logic in a way that makes it easier for someone reading your code to understand how it works and what you were trying to accomplish.