Merge remote-tracking branch 'upstream/master' into pandas-array-upstream+fu1

Author: TomAugspurger

pandas/core/arrays/base.py

@@ -180,8 +180,6 @@ def nbytes(self):
     def astype(self, dtype, copy=True):
         """Cast to a NumPy array with 'dtype'.
 
-        The default implementation only allows casting to 'object' dtype.
-
         Parameters
         ----------
         dtype : str or dtype
@@ -196,14 +194,7 @@ def astype(self, dtype, copy=True):
         array : ndarray
             NumPy ndarray with 'dtype' for its dtype.
         """
-        np_dtype = np.dtype(dtype)
-
-        if np_dtype != 'object':
-            msg = ("{} can only be coerced to 'object' dtype, "
-                   "not '{}'.").format(type(self).__name__, dtype)
-            raise ValueError(msg)
-
-        return np.array(self, dtype=np_dtype, copy=copy)
+        return np.array(self, dtype=dtype, copy=copy)
 
     def isna(self):
         # type: () -> np.ndarray

pandas/tests/extension/test_common.py

@@ -0,0 +1,67 @@
+import numpy as np
+import pytest
+
+import pandas as pd
+import pandas.util.testing as tm
+from pandas.core.arrays import ExtensionArray
+from pandas.core.dtypes.common import is_extension_array_dtype
+from pandas.core.dtypes.dtypes import ExtensionDtype
+
+
+class DummyDtype(ExtensionDtype):
+    pass
+
+
+class DummyArray(ExtensionArray):
+
+    def __init__(self, data):
+        self.data = data
+
+    def __array__(self, dtype):
+        return self.data
+
+    @property
+    def dtype(self):
+        return self.data.dtype
+
+
+class TestExtensionArrayDtype(object):
+
+    @pytest.mark.parametrize('values', [
+        pd.Categorical([]),
+        pd.Categorical([]).dtype,
+        pd.Series(pd.Categorical([])),
+        DummyDtype(),
+        DummyArray(np.array([1, 2])),
+    ])
+    def test_is_extension_array_dtype(self, values):
+        assert is_extension_array_dtype(values)
+
+    @pytest.mark.parametrize('values', [
+        np.array([]),
+        pd.Series(np.array([])),
+    ])
+    def test_is_not_extension_array_dtype(self, values):
+        assert not is_extension_array_dtype(values)
+
+
+def test_astype():
+
+    arr = DummyArray(np.array([1, 2, 3]))
+    expected = np.array([1, 2, 3], dtype=object)
+
+    result = arr.astype(object)
+    tm.assert_numpy_array_equal(result, expected)
+
+    result = arr.astype('object')
+    tm.assert_numpy_array_equal(result, expected)
+
+
+def test_astype_no_copy():
+    arr = DummyArray(np.array([1, 2, 3], dtype=np.int64))
+    result = arr.astype(arr.dtype, copy=False)
+
+    assert arr.data is result
+
+    result = arr.astype(arr.dtype)
+    assert arr.data is not result