Updates

* Use pandas_dtype
* removed cache_readonly

pandas/core/arrays/datetimes.py

@@ -12,7 +12,7 @@
     timezones)
 import pandas.compat as compat
 from pandas.errors import PerformanceWarning
-from pandas.util._decorators import Appender, cache_readonly
+from pandas.util._decorators import Appender
 
 from pandas.core.dtypes.common import (
     _NS_DTYPE, is_datetime64_dtype, is_datetime64tz_dtype, is_extension_type,
@@ -332,7 +332,7 @@ def _generate_range(cls, start, end, periods, freq, tz=None,
     def _box_func(self):
         return lambda x: Timestamp(x, freq=self.freq, tz=self.tz)
 
-    @cache_readonly
+    @property
     def dtype(self):
         if self.tz is None:
             return _NS_DTYPE

pandas/core/dtypes/dtypes.py

@@ -6,7 +6,6 @@
 
 from pandas._libs.interval import Interval
 from pandas._libs.tslibs import NaT, Period, Timestamp, timezones
-from pandas.util._decorators import cache_readonly
 
 from pandas.core.dtypes.generic import ABCCategoricalIndex, ABCIndexClass
 
@@ -532,12 +531,12 @@ def __init__(self, unit="ns", tz=None):
         self._unit = unit
         self._tz = tz
 
-    @cache_readonly
+    @property
     def unit(self):
         """The precision of the datetime data."""
         return self._unit
 
-    @cache_readonly
+    @property
     def tz(self):
         """The timezone."""
         return self._tz

pandas/core/dtypes/missing.py

@@ -209,7 +209,7 @@ def _isna_ndarraylike(obj):
             vec = libmissing.isnaobj(values.ravel())
             result[...] = vec.reshape(shape)
 
-    elif needs_i8_conversion(obj):
+    elif needs_i8_conversion(dtype):
         # this is the NaT pattern
         result = values.view('i8') == iNaT
     else:

pandas/core/internals/blocks.py

@@ -2672,11 +2672,10 @@ def _astype(self, dtype, **kwargs):
         these automatically copy, so copy=True has no effect
         raise on an except if raise == True
         """
+        dtype = pandas_dtype(dtype)
 
         # if we are passed a datetime64[ns, tz]
         if is_datetime64tz_dtype(dtype):
-            dtype = DatetimeTZDtype(dtype)
-
             values = self.values
             if getattr(values, 'tz', None) is None:
                 values = DatetimeIndex(values).tz_localize('UTC')

pandas/tests/frame/test_dtypes.py

@@ -91,8 +91,8 @@ def test_datetime_with_tz_dtypes(self):
         tzframe.iloc[1, 2] = pd.NaT
         result = tzframe.dtypes.sort_index()
         expected = Series([np.dtype('datetime64[ns]'),
-                           DatetimeTZDtype('datetime64[ns, US/Eastern]'),
-                           DatetimeTZDtype('datetime64[ns, CET]')],
+                           DatetimeTZDtype('ns', 'US/Eastern]'),
+                           DatetimeTZDtype('ns', 'CET')],
                           ['A', 'B', 'C'])
 
         assert_series_equal(result, expected)