isin([(1, 'red'), (3, 'red')]) array([ True, False, False]) For a DatetimeIndex, string values in `values` are converted to Timestamps. >>> dates = ['2000-03-11', '2000-03-12', '2000-03-13'] >>> dti = pd.to_datetime(dates) >>> dti DatetimeIndex(['2000-03-11', '2000-03-12', '2000-03-13'], dtype='datetime64[ns]', freq=None) >>> dti.isin(['2000-03-11']) array([ True, False, False]) )