As a class variable is present before any instance of the class is created, it can be used to store some meta data relevant to the class, rather than to the instances:
- fixed information like description, configuration, or identification values;
- mutable information like the number of instances created (if we add a code to increment the value of a designated variable every time we create a class instance)
A class variable is a class property that exists in just one copy, and it is stored outside any class instance. Because it is owned by the class itself, all class variables are shared by all instances of the class. They will therefore generally have the same value for every instance; butas the class variable is defined outside the object, it is not listed in the object's __dict__.
shared variable
shared variable
shared variable
contents of d1: {}
output
Conclusion: when you want to read the class variable value, you can use a class or class instance to access it.