BUG: preserve name in set_categories (#17509)

doc/source/categorical.rst

@@ -146,6 +146,8 @@ Using ``.describe()`` on categorical data will produce similar output to a `Seri
  df.describe()
  df["cat"].describe()
 
+.. _categorical.cat:
+
 Working with categories
 -----------------------
 

doc/source/whatsnew/v0.21.0.txt

@@ -566,6 +566,7 @@ Categorical
 - Bug in the categorical constructor with empty values and categories causing
  the ``.categories`` to be an empty ``Float64Index`` rather than an empty
  ``Index`` with object dtype (:issue:`17248`)
+- Bug in categorical operations with :ref:`Series.cat <categorical.cat>' not preserving the original Series' name (:issue:`17509`)
 
 PyPy
 ^^^^

pandas/core/categorical.py

@@ -2054,9 +2054,10 @@ class CategoricalAccessor(PandasDelegate, NoNewAttributesMixin):
 
  """
 
- def __init__(self, values, index):
+ def __init__(self, values, index, name):
  self.categorical = values
  self.index = index
+ self.name = name
  self._freeze()
 
  def _delegate_property_get(self, name):
@@ -2075,14 +2076,15 @@ def _delegate_method(self, name, *args, **kwargs):
  method = getattr(self.categorical, name)
  res = method(*args, **kwargs)
  if res is not None:
- return Series(res, index=self.index)
+ return Series(res, index=self.index, name=self.name)
 
  @classmethod
  def _make_accessor(cls, data):
  if not is_categorical_dtype(data.dtype):
  raise AttributeError("Can only use .cat accessor with a "
  "'category' dtype")
- return CategoricalAccessor(data.values, data.index)
+ return CategoricalAccessor(data.values, data.index,
+ getattr(data, 'name', None),)
 
 
 CategoricalAccessor._add_delegate_accessors(delegate=Categorical,

pandas/tests/test_categorical.py

@@ -57,6 +57,25 @@ def test_getitem_listlike(self):
  expected = c[np.array([100000]).astype(np.int64)].codes
  tm.assert_numpy_array_equal(result, expected)
 
+ @pytest.mark.parametrize(
+ "method",
+ [
+ lambda x: x.cat.set_categories([1, 2, 3]),
+ lambda x: x.cat.reorder_categories([2, 3, 1], ordered=True),
+ lambda x: x.cat.rename_categories([1, 2, 3]),
+ lambda x: x.cat.remove_unused_categories(),
+ lambda x: x.cat.remove_categories([2]),
+ lambda x: x.cat.add_categories([4]),
+ lambda x: x.cat.as_ordered(),
+ lambda x: x.cat.as_unordered(),
+ ])
+ def test_getname_categorical_accessor(self, method):
+ # GH 17509
+ s = pd.Series([1, 2, 3], name='A').astype('category')
+ expected = 'A'
+ result = method(s).name
+ assert result == expected
+
  def test_getitem_category_type(self):
  # GH 14580
  # test iloc() on Series with Categorical data