Introduction

• If a group of statements is repeatedly required then it is not recommended to write these statements every time separately. We have to define these statements as a single unit and we can call that unit any number of times based on our requirement without rewriting. This unit is nothing but function.
• The main advantage of functions is code reusability.

Note

• In other languages functions are known as methods procedures, subroutines …etc.

Python supports 2 types of functions

• Built in Functions
• User Defined Functions

Built in Functions

• The functions which are coming along with python software automatically, are called built in functions or pre defined functions.
• Example: id(), type(), input() …etc.

User Defined Functions

• The functions which are developed by programmer explicitly according to business requirements, are called user defined functions.

Syntax

def function_name(parameter):
  """doc string"""
  ***
  ***
  return value

Note

• While creating functions we can use 2 keywords
  • def (mandatory)
  • return (optional)

Question

Write a function to print Hello?

def wish():
  print("Hello Good Morning")
wish()
wish()
wish()

Output

Hello Good Morning
Hello Good Morning
Hello Good Morning

Parameters

• Parameters are inputs to the function. If a function contains parameters, then at the time of calling, compulsory we should provide values otherwise we will get error.

Question

Write a function to take name of the student as input and print wish message by name.

def wish(name):
  print("Hello",name," Good Morning")
wish("Ajay")
wish("Manish")

Output

Hello Ajay Good Morning
Hello Manish Good Morning

Example

Write a function to take number as input and print its square value?

def squareIt(number):
  print("The Square of",number,"is", number*number)
squareIt(4)
squareIt(5)

Output

The Square of 4 is 16
The Square of 5 is 25

Return Statement

• Function can take input values as parameters and executes business logic, and returns output to the caller with return statement.

Question

Write a function to accept 2 numbers as input and return sum?

def add(x,y):
  return x+y
result1=add(10,20)
result2=add(100,200)
print("The sum is",result1)
print("The sum is",result2)

Output

The sum is 30
The sum is 300

• If we are not writing return statement then default return value is None

Example

def f1():
  print("Hello")
f1()
print(f1())

Output

Hello
Hello
None

Question

Write a function to check whether the given number is even or odd?

def even_odd(num):
  if num%2==0:
    print(num,"is Even Number")
  else:
    print(num,"is Odd Number")
even_odd(10)
even_odd(15)

Output

10 is Even Number
15 is Odd Number

Question

Write a function to find factorial of given number?

def fact(num):
  result=1
  while num>=1:
    result=result*num
    num=num-1
  return result
for i in range(1,5):
  print("The Factorial of",i,"is :",fact(i))

Output

The Factorial of 1 is : 1
The Factorial of 2 is : 2
The Factorial of 3 is : 6
The Factorial of 4 is : 24

Returning multiple values from a function

• In other languages like C, C++ and Java, function can return maximum one value. But in python, a function can return any number of values.

Example

def sum_sub(a,b):
  sum=a+b
  sub=a-b
  return sum, sub
x, y=sum_sub(100,50)
print("The Sum is :",x)
print("The Subtraction is :",y)

Output

The Sum is : 150
The Subtraction is : 50

Example

def calc(a,b):
  sum=a+b
  sub=a-b
  mul=a*b
  div=a/b
  return sum,sub,mul,div
t=calc(100,50)
print("The Results are")
for i in t:
  print(i)

Output

The Results are
150
50
5000
2.0

Ungraded Questions

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