from pandas import ( Index, NaT, date_range, ) def test_is_monotonic_with_nat(): # GH#31437 # PeriodIndex.is_monotonic_increasing should behave analogously to DatetimeIndex, # in particular never be monotonic when we have NaT dti = date_range("2016-01-01", periods=3) pi = dti.to_period("D") tdi = Index(dti.view("timedelta64[ns]")) for obj in [pi, pi._engine, dti, dti._engine, tdi, tdi._engine]: if isinstance(obj, Index): # i.e. not Engines assert obj.is_monotonic_increasing assert obj.is_monotonic_increasing assert not obj.is_monotonic_decreasing assert obj.is_unique dti1 = dti.insert(0, NaT) pi1 = dti1.to_period("D") tdi1 = Index(dti1.view("timedelta64[ns]")) for obj in [pi1, pi1._engine, dti1, dti1._engine, tdi1, tdi1._engine]: if isinstance(obj, Index): # i.e. not Engines assert not obj.is_monotonic_increasing assert not obj.is_monotonic_increasing assert not obj.is_monotonic_decreasing assert obj.is_unique dti2 = dti.insert(3, NaT) pi2 = dti2.to_period("H") tdi2 = Index(dti2.view("timedelta64[ns]")) for obj in [pi2, pi2._engine, dti2, dti2._engine, tdi2, tdi2._engine]: if isinstance(obj, Index): # i.e. not Engines assert not obj.is_monotonic_increasing assert not obj.is_monotonic_increasing assert not obj.is_monotonic_decreasing assert obj.is_unique