MIT OpenCourseWare 6.00 Introduction to Computer Science and Programming: Lesson 7, HW 1
#!/usr/bin/env python
def nestEggFixed(salary, save, growthRate, years):
nestEgg = [salary * save * 0.01]
for year in range(1, years):
thisYear = nestEgg[year - 1] * (1 + 0.01 * growthRate) + salary * save * 0.01
nestEgg.append(thisYear)
return nestEgg
def nestEggVariable(salary, save, growthRates):
nestEgg = []
previous = 0
for rate in growthRates:
previous = previous * (1 + 0.01 * rate) + salary * save * 0.01
nestEgg.append(previous)
return nestEgg
def postRetirement(savings, growthRates, expenses):
account = []
previous = savings
for rate in growthRates:
previous = previous * (1 + 0.01 * rate) - expenses
account.append(previous)
return account
def findMaxExpenses(salary, save, preRetireGrowthRates, postRetireGrowthRates, epsilon):
savings = nestEggVariable(salary, save, preRetireGrowthRates)[-1]
low = 0
high = savings
guess = (low + high) / 2.0
endBalance = postRetirement(savings, postRetireGrowthRates, guess)[-1]
i = 1
while abs(endBalance) > epsilon and i <= 100:
if endBalance < 0:
# expenses are too high
high = guess
else:
# expenses are too low
low = guess
guess = (low + high) / 2.0
endBalance = postRetirement(savings, postRetireGrowthRates, guess)[-1]
i += 1
return guess
