Static, instance, and class methods in Python

There are three kinds of methods that can be defined within a Python class. Up until now, we have mostly been dealing with instance methods, which we have invoked with our Python class instances:

• Instance methods and variables: Any method defined within a Python class that is invoked with the instance of the class, taking the self as its first positional argument, is said to be instance method. An instance method is able to access the  instance variables and the other instance methods of the class. With the self.__class__ construct, it is also able to access the class level variables and the methods as well. An instance variable, on the other hand, is any variable that is declared within the Python class with the self keyword.
• Class methods and variables: Any method that is declared with the @classmethod Python decorator invoked with the class name is said to be a class method. A class method may also be declared without the @classmethod decorator. If this is the case, it must be invoked with the class name. A class method will have access only to the variables that are marked or declared at the class level and will not have access to object or instance level class variables. A class variable, on the other hand, can be declared outside any method. Within the class, we have to declare the variable without using the self keyword. For this reason, class variables and methods to some extent resemble static methods and variables that we studied in Java, but there is a catch, as mentioned here:

• Static methods: Any method in a Python class that is declared with the @staticmethod decorator is said to be a static method. Static methods in Python are different from what we saw in Java and C#. A static level method doesn't have access to the instance  or the object-level variables, nor to the class-level variables of the class.

Let's take an example called Class_methods.py to explain this further:

A continuation of the preceding code is shown as follows:

The preceding code snippet explains the use of static, instance, and class methods. Whenever a class method is invoked by the instance of the class, Python automatically translates the instance type to class type internally, which can be seen in line 42. 

The output is as shown in the following screenshot: