mortgage_calc.py

value = 138000
deposit = 10000
loan = value - deposit
apr = 4.5
years = 30
months = years * 12
rate = apr / 100
monthly_rate = rate / 12

"""

    The formula is M = P * ( J / (1 - (1 + J)^ -N)).
    M: monthly payment
    P: principal or amount of loan
    J: monthly interest; annual interest divided by 100, then divided by 12.
    N: number of months of amortization, determined by length in years of loan.

"""
from math import *

def find_monthly_payment(value, deposit, apr, years):
	loan = value - deposit
	months = years * 12
	rate = apr / 100
	monthly_rate = rate / 12
	monthly_payment = loan * (monthly_rate / (1-(pow((1 + monthly_rate),- months))))
	return monthly_payment
	pass

print(find_monthly_payment(138000,10000,4.5,30))