What is the difference between instance methods and class methods in Python?

Class vs. Instance Methods

Python's PEP 8 style guide recommends using "self" for instance method first arguments and "cls" for class method first arguments. Understanding the distinction between these two types of methods is crucial for effective object-oriented programming.

Instance Methods

Instance methods are associated with specific instances of a class. They operate on the instance's data and typically receive "self" as their first argument. When accessing an instance method as, for example, object.method(), the instance is automatically passed to the method.

For instance, consider the following class definition:

<code class="python">class Person:
    def __init__(self, name):
        self.name = name

    def greet(self):
        print("Hello, my name is", self.name)</code>

Here, "greet()" is an instance method that can be invoked on any instance of the "Person" class with "object.greet()".

Class Methods

Class methods, on the other hand, are associated with the class itself rather than with individual instances. They receive "cls" as their first argument, which represents the class. Class methods are used for tasks that pertain to the class as a whole, such as creating new instances or accessing class-level data.

The following code snippet illustrates a class method:

<code class="python">class Math:
    @classmethod
    def sum(cls, a, b):
        return a + b</code>

The "Math.sum()" method takes two arguments that are added together and returned. Since it's a class method, you can invoke it directly as Math.sum(1, 2) to obtain the result.

By understanding the difference between instance and class methods, developers can effectively leverage the full capabilities of object-oriented programming in Python.

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