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I use the following code in Python to price American put/call options. It's simple code since I'm new to using Quantlib. I would like to specify the contract duration (i.e. T=1, T=2, etc.) instead of specifying the calculation and maturity dates. Is it possible to do this? If so, how can I modify the code below to achieve this? 

import QuantLib as ql

def OptionPrices(T, r, sigma, K, S0, TimeSteps):
    maturity_date = ql.Date(31, 12, 2020)
    calculation_date = ql.Date(1, 1, 2020)
    ql.Settings.instance().evaluationDate = calculation_date    

    payoff = ql.PlainVanillaPayoff(ql.Option.Call, K)

    am_exercise = ql.AmericanExercise(calculation_date, maturity_date)
    american_option = ql.VanillaOption(payoff, am_exercise)

    spot_handle = ql.QuoteHandle(ql.SimpleQuote(S0))
    flat_ts = ql.YieldTermStructureHandle(ql.FlatForward(calculation_date, r, ql.Actual365Fixed()))
    dividend_yield = ql.YieldTermStructureHandle(ql.FlatForward(calculation_date, 0, ql.Actual365Fixed()))
    flat_vol_ts = ql.BlackVolTermStructureHandle(ql.BlackConstantVol(calculation_date, ql.UnitedStates(), sigma, ql.Actual365Fixed()))
    bsm_process = ql.BlackScholesMertonProcess(spot_handle, dividend_yield, flat_ts, flat_vol_ts)

    binomial_engine = ql.BinomialVanillaEngine(bsm_process, "crr", TimeSteps)
    american_option.setPricingEngine(binomial_engine)

    OptionPrices.AmCallPrices = [binomial_price(american_option, bsm_process, step) for step in range(2, TimeSteps+1, 1)]
    OptionPrices.AmCallPrice = american_option.NPV()


    payoff = ql.PlainVanillaPayoff(ql.Option.Put, K)

    american_option = ql.VanillaOption(payoff, am_exercise)

    OptionPrices.AmPutPrices = [binomial_price(american_option, bsm_process, step) for step in range(2, TimeSteps+1, 1)]
    OptionPrices.AmPutPrice = american_option.NPV()

def binomial_price(option, bsm_process, steps):
    binomial_engine = ql.BinomialVanillaEngine(bsm_process, "crr", steps)
    option.setPricingEngine(binomial_engine)
    return option.NPV()

OptionPrices(1, 0.06, 0.15, 100, 90, 200)
print(OptionPrices.AmPutPrice)

I would appreciate any help. Thanks

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1 Answer 1

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How about just defining the maturity date as todays date (or any other start date) ajusted by a period of T x 365 days? Here is an example:

T = 0.5
today = ql.Date().todaysDate()
maturity = today + ql.Period(f"{int(T*365)}d")
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  • $\begingroup$ Hello David. Thank you, it works perfectly. I appreciate your help. $\endgroup$
    – Ruan
    Commented Jan 8, 2020 at 9:32
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    $\begingroup$ ql.Period(int(T*365), ql.Days) has the same effect and might be a bit less cryptic. $\endgroup$
    – Luigi Ballabio
    Commented Jan 8, 2020 at 11:21

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