Python Function

 Python Function- Write Once, Use Many Times

Introduction

Imagine you need to calculate the sum of two numbers many times in your programs with different values.

Will you write the code again and again?

No.

Instead, you create a function in a program, that

• can have arguments, if needed
• can perform certain functionality
• can return a result

What is a Function?

A function is a block of code that performs a specific task. In Python we create functions using the def keyword.

Basic Function Syntax

def function_name():

#code

Example:

def calcSomething (x):

    r=2* x**2

    return r

a= int(input("Enter a number:"))

print(calcSomething(a))

1. Where x is the argument to function calcSomething

2. return statement returns the computed result.

3. calcSomething(a) calls the function.

Calling/Invoking/Using a Function

To use a function that has been defined earlier, you need to write a function call statement in Python. A function call statement takes the following form:

<function-name>(<value-to-be-passed-to-argument>)

For example, if we want to call the function calcSomething() defined above, our function call statement will be like :

        calcSomething(a)  #value 5 is being sent as a argument

Function with Return Value

Function can also return results.

Code:

def add(a, b):

    return a + b

result = add(5, 3)

print(result)

Output:

8

 return sends the result back.

Real-Life Example: Even or Odd

def check_even(num):

    if num % 2 ==0:

        return "Even"

    else:

        return "Odd"

print(check_even(10))

Why Use Functions?

• It gives program a clean structure.
• It is easy to debuge
• Reusable logic
• Professional coding style

Practice Questions (Very Important)

1. Create a function to find square of a number
2. Create a function to find factorial
3. Create a function to check if number is positive or negative
4. Create a function to calculate simple interest
5. Create a function to find largest of three numbers