Present Value or Future Value Calculator

Code for Present Value or Future Value Calculator

def get_initial_value():
    while True:
        value = input("Please enter the value to calculate PV/FV for: ")
        try:
            return float(value)
        except ValueError:
            print("Please enter a valid number!")

def get_pfVal():
    pfVal = input("Hello! Would you like to calculate Present Value or Future Value? Enter 0 for PV and 1 for FV: ")
    
    if pfVal == '0' or pfVal == '1':
        return pfVal
    else:
        print("Sorry, please enter 0 or 1!")
        return get_pfVal()
    
def get_periods():
    periods = input("How many discrete periods are there? Response: ")
    try:
        periods = int(periods)
        return periods
    except ValueError:
        print("Sorry, please enter a valid integer! Try again.")
        return get_periods()
    
def get_phases():
    phases = input("Enter the number of discrete growth phases (including 'none'): ").lower()
     
    if phases == "none":
        return 0
    
    else:
        try:
            phases = int(phases)
            if phases >= 0:
                return phases
            else:
                print("Sorry, please enter a non-negative integer or the word 'none'.")
                return get_phases()
            
        except ValueError:
            print("Sorry, please enter a valid integer or the word 'none'.")
            return get_phases()
    
def phaseData(phaseCount):
    phaseGrowth = []
    for i in range(phaseCount):
        growthRate = input("Input the growth rate for phase " + str(i+1) + " as a percentage (i.e., enter '6' for a rate of 6%): ")
        try:
            growthRate = float(growthRate)
        except ValueError:
            print("Please enter a valid number for the growth rate.")
            return phaseData(phaseCount)
        
        length = input("Enter the length of phase " + str(i + 1) + " in periods: ")
        try:
            length = int(length)
        except ValueError:
            print("Please enter a valid integer for the length of the phase.")
            return phaseData(phaseCount)
        
        if i == phaseCount - 1:
            ap = input("For the final phase of this problem, is it an annuity or perpetuity? Enter 'A' for annuity or 'P' for perpetuity: ").upper()
            if ap not in ["A", "P"]:
                print("Please enter 'A' for annuity or 'P' for perpetuity.")
                return phaseData(phaseCount)
            
            phaseGrowth.append({
                'growthRate': growthRate,
                'length': length,
                'type': ap
            })
        else:
            phaseGrowth.append({
                'growthRate': growthRate,
                'length': length,
                'type' : 'A'
            })
    
    return phaseGrowth

def get_rate():
    rate = input("Please enter the discount rate percentage value (i.e., enter '6' for a rate of 6%): ")
    try:
        rate = float(rate)
        return rate
    except ValueError:
        print("Please enter a VALID discount rate!")
        return get_rate()
    
def presentValue(fv, rate, periods):
    return fv / ((1 + rate/100) ** periods)

def futureValue(pv, rate, periods):
    return pv * ((1 + rate/100) ** periods)

def annuityPV(cashFlow, rate, periods):
    return cashFlow * ((1 - (1 + rate/100) ** -periods) / (rate/100))

def perpetuityPV(cashFlow, rate):
    return cashFlow / (rate/100)
    

def main():
    pfVal = get_pfVal()

    if pfVal == '0':
        print("You are calculating Present Value.")
    else:
        print("You are calculating Future Value.")

    initialValue = get_initial_value()
    print("You entered an initial value of ", initialValue, ".")

    periods = get_periods()
    print("You entered", periods, "discrete forecast periods.")

    phases = get_phases()
    print("You entered", phases, "distinct growth period(s)")

    if phases > 0:
        growthPhases = phaseData(phases)
        phaseNumber = 1
        for phase in growthPhases:
            if 'type' in phase:
                print("Phase: " + str(phaseNumber) + " Growth: " + str(phase['growthRate']) + "% Length: " + str(phase['length']) + " Type: " + str(phase['type']))
            else:
                print("Phase: " + str(phaseNumber) + " Growth: " + str(phase['growthRate']) + "% Length: " + str(phase['length']))
            phaseNumber += 1
    else:
        print("No growth phases entered.")

    rate = get_rate()
    print("You entered a discount rate of", rate, "%.")

    totalPV = 0
    totalFV = 0

    if phases == 0:
        if pfVal =='0':
            totalPV = presentValue(initialValue, rate, periods)
            print("Total PV = $", round(totalPV, 2))
        else:
            totalFV = futureValue(initialValue, rate, periods)
            print("Total FV = $", round(totalFV, 2))

    else:

        i = 0
        for phase in growthPhases:
            if 'type' in phase and phase['type'] == 'A':
                phasePV = annuityPV(initialValue, phase['growthRate'], phase['length'])
            else:
                phasePV = perpetuityPV(initialValue, phase['growthRate'])


            tempPV = presentValue(phasePV, rate, i * periods)
            tempFV = futureValue(phasePV, rate, i * periods)

            totalPV += tempPV
            totalFV += tempFV

            initialValue = tempPV if pfVal == '0' else tempFV

            i += 1

        if pfVal == '0':
            print("Total PV = $", round(totalPV, 2))

        else:
            print("Total FV = $", round(totalFV,2))
            
if __name__=="__main__": 
    main()