7.11 Class variables

An instance variable is unique to each object created by a class. A class variable is shared, accessible, and changeable by all objects of a class. There are similarities with the global variables we saw in section 6.9.2. Coders frequently use class variables instead of top level global variables. Restricting their use within a class is more acceptable, especially if their names start with “__”.

As we have seen, if obj is the name of an instance, you reference an instance variable with a name prefixed by “obj.”. obj is often self.

You define a class variable at the top level of a class, along with the instance methods.

class Guitar:
    number_of_guitars = 0

    def __init__(self, brand):
        Guitar.number_of_guitars += 1
        plural = "s" if Guitar.number_of_guitars != 1 else ""
        print(f"We have {Guitar.number_of_guitars...