Merge pull request #10922 from jreback/pop

BUG: Bug in clearing the cache on DataFrame.pop and a subsequent inplace op #10912

Author: jreback

doc/source/whatsnew/v0.17.0.txt

@@ -750,7 +750,7 @@ Bug Fixes
 - Bug in ``DataFrame.reset_index`` when index contains `NaT`. (:issue:`10388`)
 - Bug in ``ExcelReader`` when worksheet is empty (:issue:`6403`)
 - Bug in ``BinGrouper.group_info`` where returned values are not compatible with base class (:issue:`10914`)
-
+- Bug in clearing the cache on ``DataFrame.pop`` and a subsequent inplace op (:issue:`10912`)
 
 - Bug causing ``DataFrame.where`` to not respect the ``axis`` parameter when the frame has a symmetric shape. (:issue:`9736`)
 

pandas/core/generic.py

@@ -501,6 +501,11 @@ def pop(self, item):
         """
         result = self[item]
         del self[item]
+        try:
+            result._reset_cacher()
+        except AttributeError:
+            pass
+
         return result
 
     def squeeze(self):
@@ -1094,6 +1099,11 @@ def _set_as_cached(self, item, cacher):
             a weakref to cacher """
         self._cacher = (item, weakref.ref(cacher))
 
+    def _reset_cacher(self):
+        """ reset the cacher """
+        if hasattr(self,'_cacher'):
+            del self._cacher
+
     def _iget_item_cache(self, item):
         """ return the cached item, item represents a positional indexer """
         ax = self._info_axis
@@ -1330,6 +1340,7 @@ def __delitem__(self, key):
             # exception:
             self._data.delete(key)
 
+        # delete from the caches
         try:
             del self._item_cache[key]
         except KeyError:

pandas/tests/test_frame.py

@@ -5177,6 +5177,20 @@ def test_pop(self):
         self.assertNotIn('foo', self.frame)
         # TODO self.assertEqual(self.frame.columns.name, 'baz')
 
+        # 10912
+        # inplace ops cause caching issue
+        a = DataFrame([[1,2,3],[4,5,6]], columns=['A','B','C'], index=['X','Y'])
+        b = a.pop('B')
+        b += 1
+
+        # original frame
+        expected = DataFrame([[1,3],[4,6]], columns=['A','C'], index=['X','Y'])
+        assert_frame_equal(a, expected)
+
+        # result
+        expected = Series([2,5],index=['X','Y'],name='B')+1
+        assert_series_equal(b, expected)
+
     def test_pop_non_unique_cols(self):
         df = DataFrame({0: [0, 1], 1: [0, 1], 2: [4, 5]})
         df.columns = ["a", "b", "a"]