Difference between functions and methods.

Background

Let me be honest here. I always thought they are the same and used them interchangeably but as it turns out they are not. Each has it's significance or scope.  I stumbled on this question today when I started with python again after a long time. I simply googled "methods in python" and the results on different pages  were using different terminology. And that's when it struck me that methods and functions are indeed different and we should be careful to use each in proper context. I will tell what to use it context of few programming languages but lets start with the understanding process.

I believe programming can be fun.  Above is my 1st meme so please bear with me :)

Difference between Functions and Methods

 Ever tried to explain anyone what a method or function is ? You may have read some definition back in college. Anyway lets try to explain that first.

So a function has a name (called as function name). There it has the data that is passed to it that the function can operate on (called arguments). There arguments are generally provided in parenthesis "()" adjacent to the function name. And lastly there is method body that has the logic to execute when this code module is called. If you ask about a method you may probably answer the same way. 

But there is a difference. 

• Functions are standalone where as method are associated with an Object. When you call a method it is in scope of that object which has it's own blueprint (called class).  
• Another difference is that all arguments in function are explicit where as method had one implicit argument and that is reference to the object that the method belongs to. For example methods in Java can use this  in the method body or in python you can use self.

Just think of "Methods" as object oriented way of calling "Functions.

Note :  I can understand if you argue back saying what about static methods in Java? They are not associated with any instance and we definitely cannot use this in static methods. So are they still methods? Well answer is Yes. You will still call them methods. As I said "Methods" are object oriented way of calling "Functions". I know this is a lame argument but that is what it is. Do let me know in comments if you have some other view point. Would love to discuss this :)

Example in Python

I will give example in python due to which this all started for me. We can have both functions and methods in python. Hope it helps to understand this better.

Functions in python :

def test(name, place="India") :
    """ This is a test function"""
    print("Hi " + name + "! Welcome to " + place)


test("Aniket", "USA")
test("John")

Methods in python : 

class TestClass:
    def test(self, name, place="India"):
        """ This is a test method """
        print("Hi " + name + "! Welcome to " + place)

testObj = TestClass()
testObj.test("Aniket", "USA")
testObj.test("John")
 

And you should see output as (in both cases) : 

General Terminology

• For Java, there are only methods.
• For C, there are only functions.
• For C++ or Python it would depend on whether or not you're in a class.

Note : I know I have labelled this post as "programming concept" but it is more of a terminology use. There were many instance when I answered on Stack overflow using these words interchangeably and ended up corrected by someone and each time I am like "What.... how does it matter?". Well it does .. specially when you are in a circle of programmers/developers. So better late than never :)  you know now!

Related Links

• Difference between a method and a function(SO)
• Python Functions
• What is a “method” in Python?(SO)
• Functional programming(Wiki)