test_period.py 文件源码

def test_to_timestamp_pi_nat(self):
        # GH 7228
        index = PeriodIndex(['NaT', '2011-01', '2011-02'], freq='M',
                            name='idx')

        result = index.to_timestamp('D')
        expected = DatetimeIndex([pd.NaT, datetime(2011, 1, 1),
                                  datetime(2011, 2, 1)], name='idx')
        self.assertTrue(result.equals(expected))
        self.assertEqual(result.name, 'idx')

        result2 = result.to_period(freq='M')
        self.assertTrue(result2.equals(index))
        self.assertEqual(result2.name, 'idx')

        result3 = result.to_period(freq='3M')
        exp = PeriodIndex(['NaT', '2011-01', '2011-02'], freq='3M', name='idx')
        self.assert_index_equal(result3, exp)
        self.assertEqual(result3.freqstr, '3M')

        msg = ('Frequency must be positive, because it'
               ' represents span: -2A')
        with tm.assertRaisesRegexp(ValueError, msg):
            result.to_period(freq='-2A')