investments.py

def calc_savings(years=10, monthly=500, rate=1.12, initial=0.):
    """
    years = amount of years to saving money
    monthly = amount saved per month (inflation is ignored)
    rate = rate per year to apply. Must be 1 + annual interest rates
    initial = initial amount to startup
    """
    total = initial
    for n in range(years):
        total = (total + monthly * 12) * rate
        print('Year #{}:\t{}'.format(n + 1, round(total, 2)))
    return round(total, 2)

assert calc_savings(monthly=700, rate=1.12, initial=2000) == 171310.2