The principle of having a class or a function do only one thing is a very important and useful heuristic. This is known as the single responsibility principle.
Also, it is important to correctly name the classes and functions. The convention followed is to have class names be nouns and function names be verbs.
Doing these two things ensures that anyone looking at any class and function can quickly understand what it does and can plug in or remove or modify these without any issues.
For example, the below python code, which follows the above principles, is pretty easy to understand and follow along:
class ColorRetriever(object): def __init__(self): self.color = get_color() def pick(self): return self.color