# Python Simple Interest

Python is an Object-Oriented high-level language. Python has an English-like syntax, which is very easy to read and write codes. Python is an interpreted language which means that it uses an interpreter instead of the compiler to run the code.

The interpreted language is processed at the run time thus takes less time to run. Python has dynamic semantics and has high-level built-in data structures which support dynamic typing and dynamic binding. Python provides rapid development.

While learning a language, we would like to do many basic programs, one of which is calculating simple interest. Simple interest is used in banks and the financial sector to calculate interest charges on the total amount. The Simple interest is calculated on the main loan amount.

This amount is also termed as Principal. To calculate the simple interest, we need the principal amount, time period, and rate of the interest. This program is very easy to code, and we will get the knowledge of user input and operations like multiplication, division, etc.

In this post, we will discuss how to calculate the Simple Interest in Python. The formula for calculating the simple interest is:

Simple Interest = (P x R x T)/100

Where

P = Principal Amount

R = Rate of Interest

T = Time Period

Before writing the actual code, we will write the algorithm for the program. It is always wiser to write an algorithm because it makes the logic easier to understand. These are some of the advantages of algorithms:

• We can write code in any language after writing the algorithms
• Helps in debugging

So let us write the algorithms to calculate the simple interest:

``````1. Read the PrincipalPrincipal, or declare it in the code.
2. Read the Rate, or declare it in the code.
3. Read the Time, or declare it in the code.
4. Apply the formula.
5. Print the calculated Simple Interest.``````

In this post, we are going to make two programs, one in which we define all the variables in the code itself, and the other we will take the input from the user.

## Python Program

``````def Simple_Interest(P,R,T):
SI = (P*R*T)/100
return SI
P = 1000
R = 4
T = 1
SI = Simple_Interest(P,R,T)
print(“The simple Interest is: “, SI)``````

Output

``The simple interest is: 40.0`` ## Complexity

Since this program does not have any loop, and only calculation, so the complexity of this program is 0(1).

## Explanation

In the code above, we have defined the Principal amount and declared the variable as P, the value for P is 1000, the time period for the loan amount as T, the rate of interest as R.

Then we have passed these values to the function Simple_Interest, in which we are using the formula to calculate the simple interest and returning the result. In the end, we are printing the result.

## Simple Interest by User Input

In this code, we will read the values of Principal, Interest and time from the user instead of directly hard coding it.

``````def Simple_Interest(P,R,T):
SI = (P*R*T)/100
return SI
P = float(input(“Enter the Principal amount: “))
R = float(input(“Enter the Rate of Interest: “))
T = float(input(“Enter the Time Period: “))
SI = Simple_Interest(P,R,T)
print(“The simple Interest is: “, SI)``````

Output

``The simple interest is: 40.0`` ## Explanation

The only difference between this code and the above code is that in this code, we are taking inputs from a user.

In the 4,5,6 lines of code, we have taken the user input of Principal amount, rate of interest, and time period. In Python, the inputs are taken by using the input() method. The input() method reads the input as a string, so we need to convert it into either float or integer to do any mathematical operation. We are converting the input to float by using the float() method.

After this, we are again calling the function and using the formula, and printing the result.