improve performance of PandasDtype construction (lazy dtype.name)

Author: jorisvandenbossche

pandas/core/arrays/numpy_.py

@@ -43,7 +43,6 @@ class PandasDtype(ExtensionDtype):
     def __init__(self, dtype):
         dtype = np.dtype(dtype)
         self._dtype = dtype
-        self._name = dtype.name
         self._type = dtype.type
 
     def __repr__(self) -> str:
@@ -56,7 +55,7 @@ def numpy_dtype(self):
 
     @property
     def name(self):
-        return self._name
+        return self._dtype.name
 
     @property
     def type(self):

pandas/core/internals/blocks.py

@@ -70,6 +70,7 @@
     Categorical,
     DatetimeArray,
     ExtensionArray,
+    PandasArray,
     PandasDtype,
     TimedeltaArray,
 )
@@ -219,8 +220,6 @@ def array_values(self) -> ExtensionArray:
         """
         The array that Series.array returns. Always an ExtensionArray.
         """
-        from pandas.core.arrays.numpy_ import PandasArray
-
         return PandasArray(self.values)
 
     def get_values(self, dtype=None):