# Method Types In Python

In python some methods receive as a parameter the ***self\*** keyword, others the ***cls\****,* and others just nothing

## Why?

Let us first undertand the difference between class and instance

`class` is a blueprint/template for creating objects

- class is created using `class` keyword

class MyClass:
    pass

An object is created using the constructor of the class, That object is called an `Instance` of the class.

class Person:
    def greet(self):
        print('konnichiwa')

# here naruto is an object and
# naruto is an instance of the Person class
naruto = Person()
naruto.greet()
# output: "konnichiwa"

> what is constructor in python?

def __init__(self):
    pass

> In Python the `__init__()` method is called the constructor and is always called when an object is created.

Note: there are 2 types of constructors,
default and parameterized

previous example was of default constructor and this is an example of parameterized constructor

def __init__(self, data):
    self.left = None
    self.right = None
    self.data = data

# Now, let's talk about methods

There are 3 types of methods

- `Instance method`
- `Class method`
- `Static method`

class MyClass:
    def method(self):
        return 'instance method', self

    @classmethod
    def classmethod(cls):
        return 'class method', cls

    @staticmethod
    def staticmethod():
        return 'static method'

## Instance Method

The 1st method `Method` is the instance method, which is the most common method.
It needs self parameter to access attributes and other methods of the same object. It can also access the class using `self.__class__` attribute.

## Class Method

In the 2nd method classmethod, it is maked with @classmethod decorator to mark it as a classmethod.
It has a `cls` parameter which points to the class instead of object instance.

## Static Method

At the last method staticmethod, it is marked with @staticmethod decorator to mark it as a staticmethod.
It cannot modify object instance state nor class, But it can have other parameters which is applicable for other 2 methods.

#

Let's see what happens if we run these

if __name__ == '__main__':
    obj = MyClass()
    print(obj.method())
    print(obj.classmethod())
    print(obj.staticmethod())

Output:
('instance method', <__main__.MyClass object at 0x7f3cd59780d0>)

('class method', <class '__main__.MyClass'>)

static method

We can call classmethod and staticmethod like this

print(MyClass.classmethod())
print(MyClass.staticmethod())

> Output:
>
print(MyClass.classmethod())
print(MyClass.staticmethod())

So we can see instance method only needs object instance (for the self parameter)

###### tags: `python`