BUG: Bug in setting with loc/ix a single indexer and a numpy array, related to (GH3777)

Author: jreback

doc/source/release.rst

@@ -327,6 +327,7 @@ See :ref:`Internal Refactoring<whatsnew_0130.refactoring>`
   - Bug with Series indexing not raising an error when the right-hand-side has an incorrect length (:issue:`2702`)
   - Bug in multi-indexing with a partial string selection as one part of a MultIndex (:issue:`4758`)
   - Bug with reindexing on the index with a non-unique index will now raise ``ValueError`` (:issue:`4746`)
+  - Bug in setting with ``loc/ix`` a single indexer with a multi-index axis and a numpy array, related to (:issue:`3777`)
 
 pandas 0.12
 ===========

pandas/core/indexing.py

@@ -163,6 +163,10 @@ def _setitem_with_indexer(self, indexer, value):
                     labels = _safe_append_to_index(index, key)
                     self.obj._data = self.obj.reindex_axis(labels,i)._data
 
+                    if isinstance(labels,MultiIndex):
+                        self.obj.sortlevel(inplace=True)
+                        labels = self.obj._get_axis(i)
+
                     nindexer.append(labels.get_loc(key))
 
                 else:
@@ -198,33 +202,77 @@ def _setitem_with_indexer(self, indexer, value):
                 elif self.ndim >= 3:
                     return self.obj.__setitem__(indexer,value)
 
+        # set
+        info_axis = self.obj._info_axis_number
+        item_labels = self.obj._get_axis(info_axis)
+
+        # if we have a complicated setup, take the split path
+        if isinstance(indexer, tuple) and any([ isinstance(ax,MultiIndex) for ax in self.obj.axes ]):
+            take_split_path = True
+
         # align and set the values
         if take_split_path:
+
             if not isinstance(indexer, tuple):
                 indexer = self._tuplify(indexer)
 
             if isinstance(value, ABCSeries):
                 value = self._align_series(indexer, value)
 
-            info_axis = self.obj._info_axis_number
             info_idx = indexer[info_axis]
-
             if com.is_integer(info_idx):
                 info_idx = [info_idx]
+            labels = item_labels[info_idx]
+
+            # if we have a partial multiindex, then need to adjust the plane indexer here
+            if len(labels) == 1 and isinstance(self.obj[labels[0]].index,MultiIndex):
+                index = self.obj[labels[0]].index
+                idx = indexer[:info_axis][0]
+                try:
+                    if idx in index:
+                        idx = index.get_loc(idx)
+                except:
+                    pass
+                plane_indexer = tuple([idx]) + indexer[info_axis + 1:]
+                lplane_indexer = _length_of_indexer(plane_indexer[0],index)
 
-            plane_indexer = indexer[:info_axis] + indexer[info_axis + 1:]
-            item_labels = self.obj._get_axis(info_axis)
+                if is_list_like(value) and lplane_indexer != len(value):
+                    raise ValueError("cannot set using a multi-index selection indexer with a different length than the value")
+
+            # non-mi
+            else:
+                plane_indexer = indexer[:info_axis] + indexer[info_axis + 1:]
+                if info_axis > 0:
+                    plane_axis = self.obj.axes[:info_axis][0]
+                    lplane_indexer = _length_of_indexer(plane_indexer[0],plane_axis)
+                else:
+                    lplane_indexer = 0
 
             def setter(item, v):
                 s = self.obj[item]
-                pi = plane_indexer[0] if len(plane_indexer) == 1 else plane_indexer
+                pi = plane_indexer[0] if lplane_indexer == 1 else plane_indexer
 
                 # set the item, possibly having a dtype change
                 s = s.copy()
                 s._data = s._data.setitem(pi,v)
                 self.obj[item] = s
 
-            labels = item_labels[info_idx]
+            def can_do_equal_len():
+                """ return True if we have an equal len settable """
+                if not len(labels) == 1:
+                    return False
+
+                l = len(value)
+                item = labels[0]
+                index = self.obj[item].index
+
+                # equal len list/ndarray
+                if len(index) == l:
+                    return True
+                elif lplane_indexer == l:
+                    return True
+
+                return False
 
             if _is_list_like(value):
 
@@ -251,8 +299,7 @@ def setter(item, v):
                         setter(item, value[:,i])
 
                 # we have an equal len list/ndarray
-                elif len(labels) == 1 and (
-                    len(self.obj[labels[0]]) == len(value) or len(plane_indexer[0]) == len(value)):
+                elif can_do_equal_len():
                     setter(labels[0], value)
 
                 # per label values
@@ -1104,6 +1151,31 @@ def _convert_key(self, key):
 # 32-bit floating point machine epsilon
 _eps = np.finfo('f4').eps
 
+def _length_of_indexer(indexer,target=None):
+    """ return the length of a single non-tuple indexer which could be a slice """
+    if target is not None and isinstance(indexer, slice):
+        l = len(target)
+        start = indexer.start
+        stop = indexer.stop
+        step = indexer.step
+        if start is None:
+            start = 0
+        elif start < 0:
+            start += l
+        if stop is None or stop > l:
+            stop = l
+        elif stop < 0:
+            stop += l
+        if step is None:
+            step = 1
+        elif step < 0:
+            step = abs(step)
+        return (stop-start) / step
+    elif isinstance(indexer, (ABCSeries, np.ndarray, list)):
+        return len(indexer)
+    elif not is_list_like(indexer):
+        return 1
+    raise AssertionError("cannot find the length of the indexer")
 
 def _convert_to_index_sliceable(obj, key):
     """ if we are index sliceable, then return my slicer, otherwise return None """

pandas/core/internals.py

@@ -12,7 +12,8 @@
                                 is_list_like, _infer_dtype_from_scalar)
 from pandas.core.index import (Index, MultiIndex, _ensure_index,
                                _handle_legacy_indexes)
-from pandas.core.indexing import _check_slice_bounds, _maybe_convert_indices
+from pandas.core.indexing import (_check_slice_bounds, _maybe_convert_indices,
+                                  _length_of_indexer)
 import pandas.core.common as com
 from pandas.sparse.array import _maybe_to_sparse, SparseArray
 import pandas.lib as lib
@@ -563,22 +564,7 @@ def setitem(self, indexer, value):
         elif isinstance(indexer, slice):
 
             if is_list_like(value) and l:
-                start = indexer.start
-                stop = indexer.stop
-                step = indexer.step
-                if start is None:
-                    start = 0
-                elif start < 0:
-                    start += l
-                if stop is None or stop > l:
-                    stop = len(values)
-                elif stop < 0:
-                    stop += l
-                if step is None:
-                    step = 1
-                elif step < 0:
-                    step = abs(step)
-                if (stop-start) / step != len(value):
+                if len(value) != _length_of_indexer(indexer, values):
                     raise ValueError("cannot set using a slice indexer with a different length than the value")
 
         try:

pandas/tests/test_indexing.py

@@ -917,6 +917,60 @@ def f():
         #result = wp.loc[['Item1', 'Item2'], :, ['A', 'B']]
         #tm.assert_panel_equal(result,expected)
 
+    def test_multiindex_assignment(self):
+
+        # GH3777 part 2
+
+        # mixed dtype
+        df = DataFrame(np.random.randint(5,10,size=9).reshape(3, 3),
+                       columns=list('abc'),
+                       index=[[4,4,8],[8,10,12]])
+        df['d'] = np.nan
+        arr = np.array([0.,1.])
+
+        df.ix[4,'d'] = arr
+        assert_series_equal(df.ix[4,'d'],Series(arr,index=[8,10],name='d'))
+
+        # single dtype
+        df = DataFrame(np.random.randint(5,10,size=9).reshape(3, 3),
+                       columns=list('abc'),
+                       index=[[4,4,8],[8,10,12]])
+
+        df.ix[4,'c'] = arr
+        assert_series_equal(df.ix[4,'c'],Series(arr,index=[8,10],name='c',dtype='int64'))
+
+        # scalar ok
+        df.ix[4,'c'] = 10
+        assert_series_equal(df.ix[4,'c'],Series(10,index=[8,10],name='c',dtype='int64'))
+
+        # invalid assignments
+        def f():
+            df.ix[4,'c'] = [0,1,2,3]
+        self.assertRaises(ValueError, f)
+
+        def f():
+            df.ix[4,'c'] = [0]
+        self.assertRaises(ValueError, f)
+
+        # groupby example
+        NUM_ROWS = 100
+        NUM_COLS = 10
+        col_names = ['A'+num for num in map(str,np.arange(NUM_COLS).tolist())]
+        index_cols = col_names[:5]
+        df = DataFrame(np.random.randint(5, size=(NUM_ROWS,NUM_COLS)), dtype=np.int64, columns=col_names)
+        df = df.set_index(index_cols).sort_index()
+        grp = df.groupby(level=index_cols[:4])
+        df['new_col'] = np.nan
+
+        f_index = np.arange(5)
+        def f(name,df2):
+            return Series(np.arange(df2.shape[0]),name=df2.index.values[0]).reindex(f_index)
+        new_df = pd.concat([ f(name,df2) for name, df2 in grp ],axis=1).T
+
+        for name, df2 in grp:
+            new_vals = np.arange(df2.shape[0])
+            df.ix[name, 'new_col'] = new_vals
+
     def test_multi_assign(self):
 
         # GH 3626, an assignement of a sub-df to a df