Question

A group of new college graduates want to know if they save a certain amount of money every month for a certain amount of years, how much saving they are going to get after certain amount of time.

Write a python program to help them out.

Ask the user to input how much they plan to save per month; how many years (integer) they are going to keep on saving the money; every how many years do they expect to get a raise and put more money in this saving account; what’s the percentage increase to the monthly deposit; and what’s the saving account interest rate (yearly). Assume the bank distributes the interest every month. At the end of each month, the amount of money in the saving account should be:

End of the month balance = (previous end of the month balance + monthly deposit)* (1+monthly interest rate)

Display the break down details of the calculation.

Example: If the user deposit $100 per month for 2 years, and increase the deposit by 10% per year ($110 after one year) at bank interest 12% per year, show the user,

Year#, Month#, deposit, ending balance of the month

0 1 100.0 101.0

0 2 200.0 203.01

…

1 1 1310.0 1404.84

…

1 12 2520.0 2852.41

If you deposit $100 per month for 2 years, and increase the deposit by 10% per year, at bank interest 12%, you will have $2852.41 saved at the end of 2 years

Then ask the users if they want to try again, if they do, go with another iteration. If they don’t want to try again, thank the user for using the program.

What I have complete (Basically can't figure out how to calculate it, and print it):

def program_start():
print('-------------------------------------------')
print('Program main menu, please select an option:')
print('-------------------------------------------')
print('1. Begin Calculation')
print('2. Quit')
print('-------------------------------------------')
chosen_number = int(input('Enter desired option here [1, 2]: '))
if chosen_number == 1:
main()
elif chosen_number == 2:
print('Exiting...')
else:
print('-------------------------------------------')
print('Invalid selection...')
program_start()

def user_input():
initial_savings = float(input('How much do you initially plan to save?: '))
years_save = int(input('How many years do you plan to save that amount for?: '))
increase_percentage = float(input('What percent do you plan to increase each month? '))
interest = float(input('What is the interest rate yearly?: '))
return initial_savings, years_save, increase_percentage, interest
calculate(initial_savings, years_save, increase_percentage, interest)

def calculate(initial_savings, years_save, increase_percentage, interest):
INTEREST_CONSTANT = 1
end_balance = (initial_savings+increase_percentage)*(INTEREST_CONSTANT+interest)
print('End period balance is, ','$',format(end_balance,'.2f'), sep='')

def main():
initial_savings, years_save, increase_percentage, interest = user_input()
calculate(initial_savings, years_save, increase_percentage, interest)
  
program_start()

Answer 1

'''
Python version : 3.6
Python program to calculate the total savings
'''

def program_start():
   print('-------------------------------------------')
   print('Program main menu, please select an option:')
   print('-------------------------------------------')
   print('1. Begin Calculation')
   print('2. Quit')
   print('-------------------------------------------')
   chosen_number = int(input('Enter desired option here [1, 2]: '))
   if chosen_number == 1:
       main()
   elif chosen_number == 2:
       print('Exiting...')
   else:
       print('-------------------------------------------')
       print('Invalid selection...')
   # if not exit, continue  
   if chosen_number != 2:
       program_start()

def user_input():
   initial_savings = float(input('How much do you initially plan to save?: '))
   years_save = int(input('How many years do you plan to save that amount for?: '))
   increase_percentage = float(input('What percent do you plan to increase each year? '))
   interest = float(input('What is the interest rate yearly?: '))
   return initial_savings, years_save, increase_percentage, interest
  
def calculate(initial_savings, years_save, increase_percentage, interest):
   months_save = years_save*12 # calculate total months of saving
   monthly_interest = interest/1200 # calculate monthly interest
   monthly_deposit = initial_savings # set monthly deposit to initial_savings initially
   total_deposit = 0 # for storing total deposit
   year = 0
   month = 0
   num_months = 0
   balance = 0 # for staoring balance
   # print the header
   print('%10s%10s%10s%30s' %('Year#','Month#','deposit','ending balance of the month'))
   # loop that continues for months_save number of times
   while(num_months < months_save):
       num_months += 1 # increment the number of months
       # increment monthly each year, after one year
       if(num_months%13 == 0):
           monthly_deposit = monthly_deposit*(1+increase_percentage/100);
       # update the month and year
       month += 1
       if month > 12:
           month = 1
           year += 1  
      
       # add monthly_deposit to total_deposit
       total_deposit += monthly_deposit
       # calculate end balance
       balance = (balance+monthly_deposit)*(1+monthly_interest)
       # print the parameters
       print('%10d%10d%10.2f%20.2f' %(year,month,total_deposit,balance))
      
   print('\nEnd period balance is $%.2f' %balance)

def main():
   initial_savings, years_save, increase_percentage, interest = user_input()
   calculate(initial_savings, years_save, increase_percentage, interest)

program_start()  

Code Screenshot:

Output: