QuantlIb: How to use maturities in place of Tenors in OIS rate helpers Quantlib?

Question

I would like to know if I can use maturity dates from my rates dataframe to generate OISratehelpers. In the following code the OIS rate helper use 'tenors' and I want to replace those tenors with maturity dates. For 'if' conditions, it is ok to use tenors but inside calculation I want to use maturity dates. I need help in this part (ql.OISRateHelper(0, ql.Period(tenor), ql.QuoteHandle(ql.SimpleQuote(rate)), index). How can I do work with maturity dates ?

rates_df = [Curve      date        maturity    tenor  rates
         FEDFUNDS   1/10/2022     1/11/2022     1D    -0.07
         FEDFUNDS   1/10/2022     1/12/2022     2D    -0.75
         FEDFUNDS   1/10/2022     1/19/2022     1W    -0.654
         FEDFUNDS   1/10/2022     1/26/2022     2W    -0.675
         FEDFUNDS   1/10/2022     2/2/2022      3W    -0.432
         FEDFUNDS   1/10/2022     2/14/2022     1M    -0.564]
index = 'FEDFUNDS'
helpers = []   
for idx, row in rates_df.iterrows():
    rate = row["rates"] / 100
    tenor = row.tenor
    if tenor == "1D":
        helpers.append(ql.DepositRateHelper(rate, index))
    elif tenor == '2D':
         print("2D")
    else:
        helpers.append(
            ql.OISRateHelper(
                0, ql.Period(tenor), ql.QuoteHandle(ql.SimpleQuote(rate)), index
            )
        )

Answer 1

Use the DatedOISRateHelper class instead. It takes explicit start and end dates.

(The two cases—tenor and explicit dates—needed to be implemented differently in C++, so we had to write two different classes.)

Answer 2

It seems the constructor insists on a tenor. What you could perhaps try is convert the days between the maturity date and settlement date/effective date of the curve and then create a Period object from that. Please see example below:

settlement = ql.Date(10,1,2022)
maturity = ql.Date(1,11,2022)
calendar = ql.TARGET()
calendar.businessDaysBetween(settlement,maturity)
tenor = ql.Period(int(days_between),ql.Days)