Python Functions – Part 1

Posted On December 23, 2020April 20, 2021

In this article, I will be giving you an introduction to Python functions.

What is a Python function

A Python function is nothing but a block of code with a name. You can use its name to execute the code multiple times without having to write the code each time. It is similar to a method in Java except that it need not be defined within a class.

How to define a function

In order to write the code for a function, we first need to create a Python module.  You can refer to this article to understand how to create a Python module. Let us assume that we have a module functions.py.  Within this module, you can specify your first function. Consider the following code:

def add():
    num1 = int(input("Enter the first number:"))
    num2 = int(input("Enter the second number:"))
    
    result = num1+num2
    print("sum is ",result)

This code specifies a function add. You need to specify the keyword def before the function name. The function name is followed by empty parentheses. This indicates that the function does not accept any arguments.  After the parentheses, you need to specify a colon which indicates the start of the function body.  In this case, the function body consists of code that reads input numbers, adds them and prints the result.

How to invoke a function

In order to invoke the function, you simply need to specify the function name. If the function accepts any parameters, you can specify these within parentheses after the function name, otherwise you need to specify empty parentheses. You can invoke a function from another function or you can directly execute it from within a Python module. In order to directly execute the function from within a module, you just need to specify it in the module. So for example, in order to invoke the add function defined above, you can specify the following in the module:

add()

When you execute the code, it prints the following output:

Enter the first number:4
Enter the second number:7
sum is 11

Further Learning

The Python Masterclass
Everything you need to know about Python
Python for beginners
Python for finance

Conclusion

So, in this article, we understood what Python functions are. We also saw how to write a function and invoke it from within a Python module. Part 2 of this article explains about the different types of python function arguments.