In this post, we will write a program for how to calculate simple interest in Python.

First, let’s see What is Simple Interest?
Simple interest is an interest calculated on the principal amount of a loan or the original contribution to a savings account.

Simple Interest: I =  (P * R * T) / 100
Where,
I = Interest earned after T years.
P = Money borrowed or invested.
R = Annual rate of interest.
T = The length of time you borrow or invest.

Examples:

Input:
Principle=20000
Rate=2
Time=5
Output:
The simple interest is 2000.

Input:
Principle=10000
Rate=5
Time=3
Output:
The simple interest is 1500.

Let’s see the program for this:
Code version 1: Create a user defined function which will calculate and print the simple interest value.

# define a function for calculating
# simple interest
def simple_interest(p, r, t):
    
    # printing given principle amount
    print('Principal is:', p)  
    
    # printing given rate
    print('Rate is:',r) 
    
    # printing given time          
    print('Time  is:', t) 
    
    # calculating simple interest
    s = (p * t * r) / 100
    
    # printing simple interest
    print('The Simple Interest is', s) 
    
# main code
if __name__ == "__main__":
    
    # inputs
    p = 10000
    r = 6
    t = 4
    
    # function call
    simple_interest(p, r, t)

Output:

Principal is: 10000
Rate is: 6
Time  is: 4
The Simple Interest is 2400.0

Code version 2: Create a user defined one line anonymous function which will calculate and return the simple interest value using a lambda statement.

# main code
if __name__ == "__main__":
    
    # inputs
    p = 10000
    r = 6
    t = 4
    
    # printing given principle amount
    print('Principal is:', p)  
    
    # printing given rate
    print('Rate is:',r) 
    
    # printing given time          
    print('Time  is:', t) 

    # create a one line function
    # using lambda statement
    # for calculating
    # simple interest
    simple_interest = lambda p, r, t : (p * r * t) / 100

    # function call and 
    # print the return 
    # value
    print('The Simple Interest is',
          simple_interest(p, r, t))

Output:

Principal is: 10000
Rate is: 6
Time  is: 4
The Simple Interest is 2400.0