BUG: GH2745 Fix issue with indexing a series with a boolean key a 1-len list on rhs

RELEASE.rst

@@ -220,6 +220,7 @@ pandas 0.11.0
     to an *ordered* timeseries (GH2437_).
   - Fix implemented ``.xs`` when called with ``axes=1`` and a level parameter (GH2903_)
   - Timestamp now supports the class method fromordinal similar to datetimes (GH3042_)
+  - Fix issue with indexing a series with a boolean key and specifiying a 1-len list on the rhs (GH2745_)
 
 .. _GH622: https://github.com/pydata/pandas/issues/622
 .. _GH797: https://github.com/pydata/pandas/issues/797
@@ -240,6 +241,7 @@ pandas 0.11.0
 .. _GH3011: https://github.com/pydata/pandas/issues/3011
 .. _GH2681: https://github.com/pydata/pandas/issues/2681
 .. _GH2719: https://github.com/pydata/pandas/issues/2719
+.. _GH2745: https://github.com/pydata/pandas/issues/2745
 .. _GH2746: https://github.com/pydata/pandas/issues/2746
 .. _GH2747: https://github.com/pydata/pandas/issues/2747
 .. _GH2751: https://github.com/pydata/pandas/issues/2751

pandas/core/common.py

@@ -766,10 +766,6 @@ def changeit():
 
                 return r, True
 
-        new_dtype, fill_value = _maybe_promote(result.dtype,other)
-        if new_dtype != result.dtype:
-            return changeit()
-
         try:
             np.putmask(result, mask, other)
         except:

pandas/core/series.py

@@ -729,11 +729,19 @@ def where(self, cond, other=nan, inplace=False):
 
         if isinstance(other, Series):
             other = other.reindex(ser.index)
+        elif isinstance(other, (tuple,list)):
+            other = np.array(other)
         if len(other) != len(ser):
-            raise ValueError('Length of replacements must equal series length')
+
+            # GH 2745
+            # treat like a scalar
+            if len(other) == 1:
+                other = np.array(other[0]*len(ser))
+            else:
+                raise ValueError('Length of replacements must equal series length')
 
         change = ser if inplace else None
-        result, changed = com._maybe_upcast_putmask(ser,~cond,other,change=change)
+        com._maybe_upcast_putmask(ser,~cond,other,change=change)
 
         return None if inplace else ser
 

pandas/tests/test_series.py

@@ -1087,6 +1087,21 @@ def test_where(self):
         self.assertRaises(ValueError, s.where, cond[:3].values, -s)
         self.assertRaises(ValueError, s.where, cond, s[:3].values)
 
+        # GH 2745
+        s = Series([1,2])
+        s[[True, False]] = [0,1]
+        expected = Series([0,2])
+        assert_series_equal(s,expected)
+
+        s = Series([1,2])
+        s[[True, False]] = [0]
+        expected = Series([0,2])
+        assert_series_equal(s,expected)
+
+        # failures
+        self.assertRaises(ValueError, s.__setitem__, tuple([[[True, False]]]), [0,2,3])
+        self.assertRaises(ValueError, s.__setitem__, tuple([[[True, False]]]), [])
+
     def test_where_inplace(self):
         s = Series(np.random.randn(5))
         cond = s > 0