Python's Instance, Class, and Static Methods Demystified

Instance, class, and static methods each serve a distinct role in Python, and knowing when to use one over another is key to writing clean, maintainable code. Instance methods operate on individual objects using self, while class methods use cls to access class-level data. Static methods, on the other hand, provide organizational structure without relying on class or instance state.

When you understand the differences between these three method types, you’ll be in a better spot to know when to write an instance method, class method, or a static method. Ultimately, this’ll help you design better maintainable object-oriented Python code.

By the end of this tutorial, you’ll understand that:

• Instance methods access the state of a specific object through the self parameter.
• You create class methods with the @classmethod decorator and use them for operations that involve class-level data.
• You use static methods for utility functionality that doesn’t need class or instance data, and you create them with the @staticmethod decorator.
• Using class methods and static methods in your classes can improve class design and code maintainability.

Keep reading to see all three method types in action. You’ll even bake some digital pizza while working on a real-world example with all three method types in a Pizza class. If you develop an intuitive understanding for their differences, you’ll be able to write object-oriented Python code that communicates its intent more clearly and is easier to maintain in the long run.

Take the Quiz: Test your knowledge with our interactive “Python's Instance, Class, and Static Methods Demystified” quiz. You’ll receive a score upon completion to help you track your learning progress:

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Interactive Quiz

Python's Instance, Class, and Static Methods Demystified

In this quiz, you'll test your understanding of instance, class, and static methods in Python. By working through this quiz, you'll revisit the differences between these methods and how to use them effectively in your Python code.

Compare Instance Methods vs Class Methods vs Static Methods

If you’re here for a quick reminder of how the three method types differ from one another, then consider the following overview that compares them:

• Instance methods use a self parameter pointing to an instance of the class. They can access and modify instance state through self and class state through self.__class__. These are the most common methods in Python classes.

• Class methods use a cls parameter pointing to the class itself. They can modify class-level state through cls, but they can’t modify individual instance state.

• Static methods don’t take self or cls parameters. They can’t modify instance or class state directly, and you’ll mainly use them for organizational purposes and namespacing.

If you need to revisit information quickly, there’s nothing quite like a table. So here are the most important aspects of the three different types of methods in Python classes summed up in a table:

That’s enough super-condensed, repetitive reference information! If you want to know what all of this means in practice, and you like to learn by running code snippets and reasoning about them, then keep on reading.

Next, you’ll explore the differences between instance, class, and static methods in a somewhat abstract code example. Abstract you say? Don’t worry—it involves runnable code, and it’s there to set the stage for a more practical example later on.

Gain Insight Through an Abstract Example

To get warmed up, you’ll write a small Python file called demo.py with a bare-bones Python class that contains stripped-down examples of all three method types:

class DemoClass: def instance_method(self): return ("instance method called", self) @classmethod def class_method(cls): return ("class method called", cls) @staticmethod def static_method(): return ("static method called",) 

Inside demo.py, you create DemoClass—a descriptively named custom class with the sole purpose of demoing the differences between instance methods, class methods, and static methods.

Consequently, you also implement one of each of the three method types and name them accordingly. They each return a tuple containing information to help you trace what’s going on, as well as the arguments the method received, such as self and cls. The output will help you understand which objects each of the methods can access.

Now it’s time to call these demo methods in a new REPL session. Import DemoClass and create an instance of it, then start by calling the instance method:

>>> from demo import DemoClass >>> obj = DemoClass() >>> obj.instance_method() ('instance method called', <demo.DemoClass object at 0x100a30d70>) 

The output confirms that .instance_method() has access to the object instance through the self argument. Python prints the object instance as <demo.DemoClass object at 0x100a30d70>. When you call the instance method, Python replaces the self argument with the instance object, obj.

Instance methods can also access the class itself through the self.__class__ attribute. This makes instance methods powerful in terms of access restrictions. They can modify state on the object instance and on the class itself.

Next, you can try out the class method: