pivot_table strings as aggfunc

Author: bobhaffner

doc/source/whatsnew/v0.22.0.txt

@@ -326,7 +326,8 @@ Reshaping
 - Bug in :func:`DataFrame.stack` which fails trying to sort mixed type levels under Python 3 (:issue:`18310`)
 - Fixed construction of a :class:`Series` from a ``dict`` containing ``NaN`` as key (:issue:`18480`)
 - Bug in :func:`Series.rank` where ``Series`` containing ``NaT`` modifies the ``Series`` inplace (:issue:`18521`)
--
+- Bug in :func:`Dataframe.pivot_table` which fails when you pass a string for aggfunc arg (:issue:`18713`)
+- 
 
 Numeric
 ^^^^^^^

pandas/core/reshape/pivot.py

@@ -38,7 +38,9 @@ def pivot_table(data, values=None, index=None, columns=None, aggfunc='mean',
                                 fill_value=fill_value, aggfunc=func,
                                 margins=margins, margins_name=margins_name)
             pieces.append(table)
-            keys.append(func.__name__)
+            keys.append(getattr(func, '__name__', func))
+            #keys.append(func.__name__)
+
         return concat(pieces, keys=keys, axis=1)
 
     keys = index + columns

pandas/tests/reshape/test_pivot.py

@@ -1109,6 +1109,20 @@ def test_pivot_margins_name_unicode(self):
         expected = pd.DataFrame(index=index)
         tm.assert_frame_equal(table, expected)
 
+    def test_pivot_func_strings(self):
+        # GH #18713
+        f = lambda func: pivot_table(self.data, values=['D', 'E'],
+                                     index=['A', 'B'], columns='C',
+                                     aggfunc=func)
+        result = f('sum')
+        expected = f(np.sum)
+        tm.assert_frame_equal(result, expected)
+        result = f(['mean', 'std'])
+        means = f(np.mean)
+        stds = f(np.std)
+        expected = concat([means, stds], keys=['mean', 'std'], axis=1)
+        tm.assert_frame_equal(result, expected)
+
 
 class TestCrosstab(object):