raise on fillna passed a list or tuple

RELEASE.rst

@@ -105,6 +105,8 @@ pandas 0.11.1
   - Fixed bug with ``Panel.transpose`` argument aliases (GH3556_)
   - Fixed platform bug in ``PeriodIndex.take`` (GH3579_)
   - Fixed bug in reset_index with ``NaN`` in a multi-index (GH3586_)
+  - ``fillna`` methods now raise a ``TypeError`` when the ``value`` parameter
+    is a ``list`` or ``tuple``.
 
 .. _GH3164: https://github.com/pydata/pandas/issues/3164
 .. _GH2786: https://github.com/pydata/pandas/issues/2786
@@ -146,6 +148,7 @@ pandas 0.11.1
 .. _GH3493: https://github.com/pydata/pandas/issues/3493
 .. _GH3579: https://github.com/pydata/pandas/issues/3579
 .. _GH3556: https://github.com/pydata/pandas/issues/3556
+.. _GH3435: https://github.com/pydata/pandas/issues/3435
 
 
 pandas 0.11.0

doc/source/v0.11.1.txt

@@ -21,6 +21,8 @@ Enhancements
       an index with a different frequency than the existing, or attempting
       to append an index with a different name than the existing
     - support datelike columns with a timezone as data_columns (GH2852_)
+  - ``fillna`` methods now raise a ``TypeError`` if the ``value`` parameter is
+    a list or tuple.
 
 See the `full release notes
 <https://github.com/pydata/pandas/blob/master/RELEASE.rst>`__ or issue tracker
@@ -31,3 +33,4 @@ on GitHub for a complete list.
 .. _GH3477: https://github.com/pydata/pandas/issues/3477
 .. _GH3492: https://github.com/pydata/pandas/issues/3492
 .. _GH3499: https://github.com/pydata/pandas/issues/3499
+.. _GH3435: https://github.com/pydata/pandas/issues/3435

pandas/core/frame.py

@@ -3319,7 +3319,7 @@ def fillna(self, value=None, method=None, axis=0, inplace=False,
         value : scalar or dict
             Value to use to fill holes (e.g. 0), alternately a dict of values
             specifying which value to use for each column (columns not in the
-            dict will not be filled)
+            dict will not be filled). This value cannot be a list.
         axis : {0, 1}, default 0
             0: fill column-by-column
             1: fill row-by-row
@@ -3341,6 +3341,9 @@ def fillna(self, value=None, method=None, axis=0, inplace=False,
         -------
         filled : DataFrame
         """
+        if isinstance(value, (list, tuple)):
+            raise TypeError('"value" parameter must be a scalar or dict, but '
+                            'you passed a "{0}"'.format(type(value).__name__))
         self._consolidate_inplace()
 
         axis = self._get_axis_number(axis)

pandas/core/panel.py

@@ -1007,6 +1007,9 @@ def fillna(self, value=None, method=None):
         --------
         DataFrame.reindex, DataFrame.asfreq
         """
+        if isinstance(value, (list, tuple)):
+            raise TypeError('"value" parameter must be a scalar or dict, but '
+                            'you passed a "{0}"'.format(type(value).__name__))
         if value is None:
             if method is None:
                 raise ValueError('must specify a fill method or value')

pandas/core/series.py

@@ -2729,6 +2729,9 @@ def fillna(self, value=None, method=None, inplace=False,
         -------
         filled : Series
         """
+        if isinstance(value, (list, tuple)):
+            raise TypeError('"value" parameter must be a scalar or dict, but '
+                            'you passed a "{0}"'.format(type(value).__name__))
         if not self._can_hold_na:
             return self.copy() if not inplace else None
 

pandas/tests/test_frame.py

@@ -6039,6 +6039,12 @@ def test_fillna_invalid_method(self):
         except ValueError, inst:
             self.assert_('ffil' in str(inst))
 
+    def test_fillna_invalid_value(self):
+        # list
+        self.assertRaises(TypeError, self.frame.fillna, [1, 2])
+        # tuple
+        self.assertRaises(TypeError, self.frame.fillna, (1, 2))
+
     def test_replace_inplace(self):
         self.tsframe['A'][:5] = nan
         self.tsframe['A'][-5:] = nan

pandas/tests/test_panel.py

@@ -1099,6 +1099,9 @@ def test_fillna(self):
         self.assertRaises(ValueError, self.panel.fillna)
         self.assertRaises(ValueError, self.panel.fillna, 5, method='ffill')
 
+        self.assertRaises(TypeError, self.panel.fillna, [1, 2])
+        self.assertRaises(TypeError, self.panel.fillna, (1, 2))
+
     def test_ffill_bfill(self):
         assert_panel_equal(self.panel.ffill(),
                            self.panel.fillna(method='ffill'))

pandas/tests/test_series.py

@@ -3822,6 +3822,11 @@ def test_fillna_int(self):
         s.fillna(method='ffill', inplace=True)
         assert_series_equal(s.fillna(method='ffill', inplace=False), s)
 
+    def test_fillna_raise(self):
+        s = Series(np.random.randint(-100, 100, 50))
+        self.assertRaises(TypeError, s.fillna, [1, 2])
+        self.assertRaises(TypeError, s.fillna, (1, 2))
+
 #------------------------------------------------------------------------------
 # TimeSeries-specific