Problem Set 1B

# -*- coding: utf-8 -*-
"""
Created on Thu Aug 11 16:32:59 2022

@author: vixey foxwish
"""
# See Problem Set 1A file for prior context
# Part B: Saving, with a raise

# In Part A, we unrealistically assumed that your salary didn't change. But 
# clearly you are going to be worth more to your company over time. So we are
# going to build on your solution to Part A by factoring in a raise every six
# months. In ps1b.py, copy your solution to Part A (as we are going to reuse 
# much of that machinery.) Modify your program to include the following:
    # 1. Have the user input a semi-annual salary raise semi_annual_raise
    # (as a decimal percentage)
    # 2. After the 6th month, increase your salary by that percentage. Do the 
    # same after the 12th month, 18th month, and so on.
# Write a program to calculate how many months it will take you to save up enough 
# money for a down payment. Like before, assume that your investments earn a return
# of r = 0.04 
 # my note: (simplified, non-adjusted approximated monthly return of .04/12) 
# and the required down payment percentage is 0.25 or 25%. Have the user enter
# the following variables:
    # 1. The starting annual salary (annual_salary) 2
    # 2. The percentage of salary to be saved (portion_saved) 
    # 3. The cost of your dream home (total_cost) 
    # 4. The semiannual salary raise (semi_annual_raise)
portion_down_payment = 0.25
r = 0.04
current_savings = 0
month_count = 0
annual_salary = float(input("Enter your annual salary: \n"))   
portion_saved = float(input("Enter the percent of your salary to save, as a decimal: \n"))
total_cost = float(input("Enter the cost of your dream home: \n"))
semi_annual_raise = float(input("Enter the semi-annual raise, as a decimal: \n"))

down_required = portion_down_payment*total_cost
monthly_unadjusted_return = r/12
# This doesn't account for true r compounding 1.04^(1/12) and is just .04/12 monthly instead

while current_savings < down_required:
    month_count += 1
# This starts the month increment increasing by 1 before end of the month changes   
    monthly_gain = current_savings*monthly_unadjusted_return
 # This is the gain caused by the monthly return on previously saved funds   
    current_savings += monthly_gain
    monthly_contribution = annual_salary*(1/12)*portion_saved
# This is the newly added money from the salary being added at end of month
# (There hasn't been any time elapsed for investment gains, so it comes separately)    
    current_savings += monthly_contribution
# Note that semi-annual raise can only take effect "AFTER" the 6th/12th/18th/etc. month    
    if (month_count%6 == 0):
# Code checks that number of months elapsed by now is evenly divisible by 6, then *= applies raise        
        annual_salary *= (1+semi_annual_raise)
print("Number of months: ", month_count)    
# Verified that (120,000; .05; 1,000,000; .03) returns 142 months as in HW answers
# Verified that (80,000; .1; 800,000; .03) returns 159 months as in the HW answers
# Verified that (75,000; .05; 1,500,000; .05) returns 261 months as in the HW answers