BUG: handle lists too in DataFrame.xs when partially selecting data from DataFrame. close #1796

Author: wesm

RELEASE.rst

@@ -197,6 +197,8 @@ pandas 0.9.0
   - Set index names in DataFrame.from_records (#1744)
   - Fix time series indexing error with duplicates, under and over hash table
     size cutoff (#1821)
+  - Handle list keys in addition to tuples in DataFrame.xs when
+    partial-indexing a hierarchically-indexed DataFrame (#1796)
 
 pandas 0.8.1
 ============

pandas/core/index.py

@@ -2081,7 +2081,12 @@ def _drop_levels(indexer, levels):
 
         level = self._get_level_number(level)
 
+        # kludge for #1796
+        if isinstance(key, list):
+            key = tuple(key)
+
         if isinstance(key, tuple) and level == 0:
+
             try:
                 if key in self.levels[0]:
                     indexer = self._get_level_indexer(key, level=level)

pandas/tests/test_multilevel.py

@@ -312,6 +312,22 @@ def test_xs_partial(self):
         assert_frame_equal(result, expected)
         assert_frame_equal(result, result2)
 
+        result = self.ymd.xs((2000, 4))
+        expected = self.ymd.ix[2000, 4]
+        assert_frame_equal(result, expected)
+
+        # ex from #1796
+        index = MultiIndex(levels=[['foo', 'bar'], ['one', 'two'], [-1, 1]],
+                           labels=[[0, 0, 0, 0, 1, 1, 1, 1],
+                                   [0, 0, 1, 1, 0, 0, 1, 1],
+                                   [0, 1, 0, 1, 0, 1, 0, 1]])
+        df = DataFrame(np.random.randn(8, 4), index=index,
+                       columns=list('abcd'))
+
+        result = df.xs(['foo', 'one'])
+        expected = df.ix['foo', 'one']
+        assert_frame_equal(result, expected)
+
     def test_xs_level(self):
         result = self.frame.xs('two', level='second')
         expected = self.frame[self.frame.index.get_level_values(1) == 'two']