interest.py

def pay(current_debt, amount):
    return current_debt-amount

def next_year(previous_debt, amount, n):
    if previous_debt <= 0:
        return n
    previous_debt = previous_debt + 0.068*previous_debt
    previous_debt = pay(previous_debt, amount)
    print previous_debt
    return next_year(pay(previous_debt, amount), amount, n+1)

print next_year(32000, 3000, 1)