Problema de finanza #1

psf1.py

import unittest

"""
Implement a class Finances, which contains a function timeLeft.  timeLeft is
passed three int values: initialValue, interest, monthly.

* The initial value of the bank account is initialValue.  
* Interest is compounded monthly at a rate of interest percent.
* Every month monthly dollars is taken out from the account (immediately after
	the Interest has been added).  
* timeLeft must return an int that is the number of months the account can 
	support the full monthly withdrawal.  
* If the account will last longer than 1200 months, the function should return 1200.
"""

class Finances(object):

	def __init__(self, debug = False):
		self.debug = debug

	def _validate(self, value, minLim, maxLim):
		return minLim if value < minLim else maxLim if value > maxLim else value

	def timeLeft(self, initialValue, interest, monthly):
		initialValue = self._validate(initialValue, 0, 100000)
		interest = self._validate(interest, 0, 1000)
		monthly = self._validate(monthly, 0, 100000)
		months = 0
		while initialValue > 0:
			if self.debug != False:
				print months, initialValue, interest, monthly
			initialValue -= monthly + (monthly * (float(interest)/100))
			if initialValue < 0: 
				break
			months+=1
		return months if months < 1200 else 1200		

class TestFinancialCases(unittest.TestCase):

	def test_first(self):
		f = Finances()
		self.assertEqual(1, f.timeLeft(100,0,100))

	def test_second(self):
		f = Finances()
		self.assertEqual(0, f.timeLeft(200,1,300))

	def test_third(self):
		f = Finances()
		self.assertEqual(1200, f.timeLeft(3452, 8, 200))

if __name__ == '__main__':
	unittest.main()