Python Functions

Hey Guys Welcome to our New blog post today we will discuss about python functions and in python functions we will learn many features of python and also learn how to use functions.

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In previous blog post we discuss about the Python List in which we learn various Functions of List so if you want to learn Python or Python Lists You can visit Our previous Blog - Python Lists

In Today's Blog

In Today's Blog We Will Learn About the Python Functions now without any delay let's start today's blog.

Contents -

Functions
Types of Functions

Built in Functions
User Defined Functions

Importance of Functions
How to Define Functions
Parameters
Type of Parameters

Formal
Actual
Default

User Defined Functions

Functions without Parameters
Functions with Parameters

Example of Actual and Formal Parameters
Concept of Default Parameters
Passing parameters

Positional
Default
Keyword

Returning values from Functions
Scope and lifetime of variable

local scope
global scope

Functions

Functions are the sub-programs that perform specific task.

Functions are the small modules and in each module you can perform specific task.

*Module - Component/Part

Types of Functions

In Python there are mainly two type of functions -

Built in Functions

Built in functions are those functions which loaded automatically with the python language.

for example - input() or len() or max()

User Defined Functions

User defined functions are those functions which is defined by the user according to their desire.

Importance of User Defined Functions

Re-usability

Once the function body is defined it can be use more than one time as per user choice.

Modularity

In simple words modularity means a complex problem can be divided into small parts.

How to Define Functions

It is very simple we can define functions just by adding def keyword in the starting of the program.

for example -

def sum( ):

In the above example the def refers to define and the sum( ) is the function we want to define.

def sum( ):

a=int(input("Enter 1st Number"))

b=int(input("Enter 2nd Number"))

c=a+b

print(c)

sum( )

In the above example we see that we just defined a function named sum and after writing the function we write program to calculate the sum of two numbers as we write in our normal python IDLE.

But you notice that after writing the whole program we write three times sum( ) which is our function name.

So by writing three times sum( ) after the function when we run the program then the function will automatically runs three times because we write three times sum.

If we write two times then it runs automatically two times.

Parameters

Parameters are the variables used to pass values from one function to another function.

Type of Parameters

Formal Parameters

Formal Parameters are written in the function prototype or with function header of the definition.

These variables will be treated as local variable of the function.

for example - def sum(x,y)

Actual Parameters

These are the variables through which actual values will be passed, when we are calling the function.

for example - sum(5,4)

Default Parameters

These are the parameters with default values.

for example - def sum(x,y=5)

User Defined Functions

Now there are two types of user defined functions -

Functions Without Parameters

These are the functions without the value inside parenthesis.

for example -

def sum( ):

a=int(input("Enter 1st Number"))

b=int(input("Enter 2nd Number"))

c=a+b

print(c)

sum( )

In the above example after defining the function in the function sum( ) we did not give the value inside the function.

Function Without Parameters

These are the functions with the value inside the function.

Example of Actual and Formal Parameters

formal parameters

⇲ ⭹

def sum(a,b):

c=a+b

print(c)

x=int(input("Enter 1st Number"))

y=int(input("Enter 2nd Number"))

sum(x,y)

⇱ ↗

Actual Parameters

Concept of Default Parameters

def sum(x,y=5):

z=x+y

print(z)

a=int(input("Enter 1st Number"))

b=int(input("Enter 2nd Number"))

sum(a,b)

sum(a)

sum( ) ❌ -this statement sum( ) is wrong statement in the default parameters because above we already give 4 variables x,y and a,b.

Passing Parameters

Python has three ways to pass the values through arguments.

Positional Argument

It follows the sequence of variable declaration.

for example -

def sum(a,b,c):

d=a+b+c sum(a,b,c)

print(d) ↓ ↓ ↓

sum(5,6,7)

sum(7,6,5)

Default Argument

In a function header any parameter cannot have a default value unless all parameters appearing on its right have their default values.

for example -

def simpleintrest(p,r,t=2):

si=(p*r*t)/100

print(si)

simpleintrest(1000,10)

we need to enter all the three values of p r t in the definition then only the program will run.

def si(p,r=10,t) ❌ - wrong Statement

def si(p=1000,r=10,t) ❌ - wrong Statement

def si(p=1000,r=10,t=2) ✔️ - correct Statement

Keyword Argument

In this argument sequence does not matter and the values are received by the names.

for example -

def simple_interest(p,r,t):

si=p*r*t/100

print(si)

simple_interest(p=1000,r=10,t=2)

simple_interest(p=1000,t=2,r=10)

simple_interest(r=10,t=2,p=1000)

Returning Values from Function

Functions in python may or may not return value it can be classified in two ways -

Function Returning Some Value -

def sum(a,b):

c=a+b

return c

result=sum(2,3)

print(result)

Function not returning any value

def sum(a,b):

c=a+b

return c

result=sum(2,3)

print(result)

Scope and lifetime of variable

Local Scope

Local Scope are the variables which are used inside the function and they are destroyed once.

Hence, the function does not remember the value of a variable from its previous call.

for example -

def square( ):

x=5

print("local variable",x)

x=10

square( )

print("variable outside function square")

here variable x declared inside square( ) will be treated as local variable and it cannot be accessed outside.

Global Scope

Global Scope are the variables which can used outside the function.

In this scope, lifetime of a variable is the period through which the variable exists in the memory.

for example -

glv=10

def global_variable( ):

print("inside function",glv)

global_variable( )

print("outside function",glv)

here we can see the variable glv can be used anywhere either inside or outside the function.

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Python Functions