Changed __sub__ to difference

Author: benthayer

doc/source/groupby.rst

@@ -134,7 +134,7 @@ but the specified columns
 .. ipython:: python
 
    df.set_index(['A', 'B'])
-   grouped = df.groupby(level=df.index.names - ['B'])
+   grouped = df.groupby(level=df.index.names.difference(['B'])
 
 These will split the DataFrame on its index (rows). We could also split by the
 columns:

pandas/indexes/frozen.py

@@ -31,13 +31,6 @@ def __add__(self, other):
 
     __iadd__ = __add__
 
-    def __sub__(self, other):
-        other = set(other)
-        temp = [x for x in self if x not in other]
-        return self.__class__(temp)
-
-    __isub__ = __sub__
-
     # Python 2 compat
     def __getslice__(self, i, j):
         return self.__class__(super(FrozenList, self).__getslice__(i, j))
@@ -87,6 +80,11 @@ def __repr__(self):
     __setitem__ = __setslice__ = __delitem__ = __delslice__ = _disabled
     pop = append = extend = remove = sort = insert = _disabled
 
+    def difference(self, other):
+        other = set(other)
+        temp = [x for x in self if x not in other]
+        return self.__class__(temp)
+
 
 class FrozenNDArray(PandasObject, np.ndarray):
 

pandas/tests/indexes/test_frozen.py

@@ -23,29 +23,22 @@ def test_add(self):
         expected = FrozenList([1, 2, 3] + self.lst)
         self.check_result(result, expected)
 
-    def test_sub(self):
-        result = self.container - [2]
-        expected = FrozenList([1, 3, 4, 5])
-        self.check_result(result, expected)
-
-    def test_sub_dupe(self):
-        result = FrozenList([1, 2, 3, 2]) - [2]
-        expected = FrozenList([1, 3])
-        self.check_result(result, expected)
-
     def test_inplace_add(self):
         q = r = self.container
         q += [5]
         self.check_result(q, self.lst + [5])
         # other shouldn't be mutated
         self.check_result(r, self.lst)
 
-    def test_inplace_sub(self):
-        q = r = self.container
-        q -= [5]
-        self.check_result(q, self.container - [5])
-        # other shouldn't be mutated
-        self.check_result(r, self.lst)
+    def test_difference(self):
+        result = self.container.difference([2])
+        expected = FrozenList([1, 3, 4, 5])
+        self.check_result(result, expected)
+
+    def test_difference_dupe(self):
+        result = FrozenList([1, 2, 3, 2]).difference([2])
+        expected = FrozenList([1, 3])
+        self.check_result(result, expected)
 
 
 class TestFrozenNDArray(CheckImmutable, CheckStringMixin, tm.TestCase):