Functions in Python

February 18, 2021

Functions in Python

The function is a block of related statements that performs a specific task when it is called.

Functions helps in breaking our program into smaller and modular chunks which makes our program more organized and manageable. Also, it avoids repetition and makes the code reusable.

Types of Function

Functions in python can be divided into two types

Built-in Functions : Functions that are built into Python.
User-defined Functions : Functions defined by the users themselves.

# function
def square( n ):
    return n ** 2

# calling function
print( square( 2 ))
print( square( 3 ))
print( square( 4 ))

Output :

4
9
16

The pass Statement

The pass statement is used to avoid getting an error in empty functions as function definitions can not be empty in python.

#function defination
def simle():
    pass

Docstring

The first string after the function header is called the docstring and is short for documentation string.

#doc_string
def docString():
    “This is a docstring of the function docString()”
    
#calling function doc()
print(docString.__doc__)

Output :

This is a docstring of the function docString()

Default Parameters

If we call the function without argument, it uses the default value.

#function
def add(a=10,b=20):
    print(“Sum of a =”,a,“and b =”,b,” is “,a+b)

#calling function without any parameter
#a and b will be default
add()

#calling function with only one parameter
#a=30 and b will be default
add(30)

#calling function with only one parameter
#b=30 and a will be default
add(b=50)

#calling function with both the parameters
#a=100 and b=200
add(100,200)

Output :

Sum of a = 10 and b = 20  is  30
Sum of a = 30 and b = 20  is  50
Sum of a = 10 and b = 50  is  60
Sum of a = 100 and b = 200  is  300

Keyword Parameters

To allow the caller to specify the argument name with values so that caller does not need to remember the order of parameters.

#function
def hello(fname, lname, score):
    print(“Hello”,fname, lname, “. Your score is”,score)

#calling function
hello(lname=“Salampuria”,fname=“Muskan”, score=“100”)
hello(fname=“Vaibhav”, score=“99”, lname=“Kumar”)
hello(score=“10”, lname=“xyz”, fname=“abc”)

Output :

Hello Muskan Salampuria . Your score is 100
Hello Vaibhav Kumar . Your score is 99
Hello abc xyz . Your score is 10

Arbitrary Parameters

If we are not sure with number of arguments that will be passed in our function, we can use * before the parameter name so that the function will receive a tuple of arguments, and we can access the items accordingly.

#function
def welcome( *names ):
    print(“\n Total number of names are : “,len(names))
    for n in names:
        print(“Welcome”,n )


# Passing 6 parameters
welcome(“Saz”,“Joe”,“Hena”,“Justin”,“Karx”,“Max”)

# Passing 3 parameters
welcome(“Sufi”,“Sana”,“Muskan”)

Output :

Total number of names are :  6
Welcome Saz
Welcome Joe
Welcome Hena
Welcome Justin
Welcome Karx
Welcome Max

Total number of names are :  3
Welcome Sufi
Welcome Sana
Welcome Muskan