With that code below, i can generate a dataframe with all business days between two dates, but i dont know how to filter to only be included in dataframe the first business day of each month.

class Feriados_SP(AbstractHolidayCalendar):
    rules = [
        Holiday('Confraternização Universal', month=1, day=1),
        Holiday('Aniversário de São Paulo', month=1, day=25),
        Holiday('Segunda-Feira de Carnaval', month=1, day=1, offset=[Easter(), Day(-48)]),
        Holiday('Terça-Feira de Carnaval', month=1, day=1, offset=[Easter(), Day(-47)]),
        Holiday('Quarta-Feira de Cinzas', month=1, day=1, offset=[Easter(), Day(-46)]),
        # Sexta-feira Santa
        GoodFriday,
        Holiday('Corpus Christi', month=1, day=1, offset=[Easter(), Day(60)]),
        Holiday('Tiradentes', month = 4, day = 21),
        Holiday('Dia do Trabalho', month = 5, day = 1),
        Holiday('Revolução Constitucionalista', month=7, day=9, start_date='1997-01-01'),
        Holiday('Independência do Brasil', month = 9, day = 7),
        Holiday('Nossa Senhora Aparecida', month = 10, day = 12),
        Holiday('Finados', month = 11, day = 2),
        Holiday('Proclamação da República', month = 11, day = 15),
        Holiday('Dia da Consciencia Negra', month=11, day=20, start_date='2004-01-01'),
        Holiday('Vespera de Natal', month=12, day=24),
        Holiday('Natal', month = 12, day = 25)]

sp_cal = Feriados_SP()
feriados_sp = sp_cal.holidays(datetime(2000, 12, 31), datetime(2079, 12, 31))
start = datetime(2024, 3, 1)
end = datetime(2025, 5, 5)
datas = pd.bdate_range(start, end, freq='C', holidays=feriados_sp)
print(datas)

I want to see a code that generates a dataframe with only the first business day of each month between two given dates.
Ive seen that using standart business day calendar using is_month_start function,

by adding this to the code:

primeiros_dias_uteis = datas[datas.is_month_start]
df = pd.DataFrame({‘Datas’: primeiros_dias_uteis})
print(df)

but it gives me the following error:

ValueError: Custom business days is not supported by is_month_start.