Combining two pandas series with changing logic
First, we know for sure that result is always False when s2 is False, and always True when both s1 and s2 are True. That does not depend on previous values:
x.loc[~x['s2'], 'result'] = Falsex.loc[x['s1'] & x['s2'], 'result'] = TrueThen we fill NA's with "forward fill":
x['result'].fillna(method = 'ffill', inplace = True)And in case there are some NA's remaining at the beginning of the column, we replace them with False:
x['result'].fillna(False, inplace = True)