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1. Print "Hello, World!"2. Add Two Numbers3. Swap Two Variables4. Find ASCII Value of a Character5. Check Even or Odd6. Find Largest of Two Numbers7. Find Largest of Three Numbers8. Check Positive, Negative, or Zero9. Convert Kilometers to Miles10. Convert Celsius to Fahrenheit11. Calculate Area of a Triangle12. Calculate Simple Interest13. Calculate Compound Interest14. Calculate Square Root15. Convert Seconds to Hours, Minutes, and Seconds16. Calculate Body Mass Index (BMI)17. Check Leap Year18. Find Absolute Value19. Calculate Age from Birth Year20. Sum of First N Natural Numbers21. Calculate Power Without Using pow()22. Print Multiplication Table23. Convert Decimal to Binary24. Convert Binary to Decimal25. Calculate Electricity Bill

Calculate Compound Interest in Python

A = P(1 + R/100n)^(nT). Then interest is A minus P. The ** is the whole point.

BeginnerBasic Python ProgramsExample 13 of 25
calculate-compound-interest.py
1# Program to calculate compound interest
2

3principal = float(input("Enter principal amount: "))
4rate = float(input("Enter annual interest rate (in %): "))
5time = float(input("Enter time in years: "))
6n = int(input("Enter number of times interest applied per year: "))
7

8amount = principal * (1 + rate / (100 * n)) ** (n * time)
9compound_interest = amount - principal
10

11print("Compound Interest is:", compound_interest)
12print("Total Amount is:", amount)

Output

Enter principal amount: 1000
Enter annual interest rate (in %): 5
Enter time in years: 2
Enter number of times interest applied per year: 4
Compound Interest is: 104.486... 
Total Amount is: 1104.486...

In this one

  • ** is power, ^ is XOR
  • print A - P, not just A

What's going on

Simple interest is a multiply. Compound interest is a power.

A = P * (1 + R/(100*n)) ** (n*T)

n is "how many times a year". Quarterly → 4. Forget it and you are back to simple-ish interest.

Interest is A - P, not A. Printing only the amount makes people think they earned 1104 rupees on a 1000 principal.

** is exponent. ^ is XOR. Use the wrong one and you get a mystery integer.

After this program

If the idea is still fuzzy, read Day 1: Introduction to Python in the Python course. For a short check, try the Python quiz (300 questions). Stay with all 25 basic python programs, or see every topic on Python exercises.

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