PS4: Problems 1–3 » Solutions

[aranthe]

Sorry these are late! I completely forgot that it was due this week.

Note: To simply readability, I've removed all of the triple-quoted comments found in the template and will post problem 4 separately because it's longer.

PS4 » Problem 1

def nestEggFixed(salary, save, growthRate, years):

    assert salary > 0, 'Salary must be greater than 0:' + str(salary)
    assert 0 < save < 100, 'Savings percentage must be between 0 and 100:' + str(savePct)
    assert 0 < growthRate < 100, 'Growth rate must be greater than 0:' + str(growthPct)
    assert years > 0, 'Years must be greater than 0:' + str(years)

    savingsRecord = [] # Initialize savings list.

    # Add one to years to capture last year.
    for year in range( 1, years+1 ):

        # First year is different.
        if( year == 1 ):
            savingsRecord.append( salary * save * 0.01 )
        else:
            # savingsRecord[-1] is the savings at the end of the last year.
            savingsRecord.append( savingsRecord[-1] * (1 + 0.01 * growthRate) + salary * save * 0.01 )
    return savingsRecord

PS4 » Problem 2

def nestEggVariable(salary, save, growthRates):

    assert salary > 0, 'Salary must be greater than 0:' + str(salary)
    assert 0 < save < 100, 'Savings percentage must be between 0 and 100:' + str(savePct)

    savingsRecord = [] # Initialize savings list.
    years = len(growthRates) # Compute number of years from input variable.
    
    # Add one to years to capture last year.
    for year in range( 1, years+1 ):
        
        # First year is different.
        if( year == 1 ):
            savingsRecord.append( salary * save * 0.01 )
        else:
            # savingsRecord[-1] is the savings at the end of the last year.
            savingsRecord.append( savingsRecord[-1] * (1 + 0.01 * growthRates[year-1]) + salary * save * 0.01 )
    return savingsRecord

PS4 » Problem 3

def postRetirement(savings, growthRates, expenses):

    assert savings > 0, 'Savings must be greater than 0:' + str(savings)

    fundBalances = [] # Initialize fund list.
    years = len(growthRates) # Compute number of years from input variable.
    
    # Add one to years to capture last year.
    for year in range( 1, years+1 ):
        
        # First year is different.
        if( year == 1 ):
            fundBalances.append( savings * (1 + 0.01 * growthRates[year-1]) - expenses )
        else:
            # fundBalances[-1] is the fund at the end of the last year.
            fundBalances.append( fundBalances[-1] * (1 + 0.01 * growthRates[year-1]) - expenses )
    return fundBalances