a panel constructed with a None value throws an error (0.9 exhibits the same behavior)

Python 2.7.3 (default, Jun 21 2012, 07:50:29)
[GCC 4.4.5] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import pandas
>>> print pandas.__version__
0.8.1
>>> print pandas.Panel(dict(a = None, b = pandas.DataFrame(index=[1,2,3],columns=[1,2,3])))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.7/site-packages/pandas-0.8.1-py2.7-linux-x86_64.egg/pandas/core/panel.py", line 219, in __init__
    mgr = self._init_dict(data, passed_axes, dtype=dtype)
  File "/usr/local/lib/python2.7/site-packages/pandas-0.8.1-py2.7-linux-x86_64.egg/pandas/core/panel.py", line 256, in _init_dict
    major = _extract_axis(data, axis=0)
  File "/usr/local/lib/python2.7/site-packages/pandas-0.8.1-py2.7-linux-x86_64.egg/pandas/core/panel.py", line 1396, in _extract_axis
    raw_lengths.append(v.shape[axis])
AttributeError: 'NoneType' object has no attribute 'shape'

added tests and fixes for this case (and the pathological case of constructing with dict(a=None))

Author: jreback

pandas/core/panel.py

@@ -1409,8 +1409,11 @@ def _homogenize_dict(frames, intersect=True, dtype=None):
     columns = _extract_axis(adj_frames, axis=1, intersect=intersect)
 
     for key, frame in adj_frames.iteritems():
-        result[key] = frame.reindex(index=index, columns=columns,
-                                    copy=False)
+        if frame is not None:
+            result[key] = frame.reindex(index=index, columns=columns,
+                                        copy=False)
+        else:
+            result[key] = None
 
     return result, index, columns
 
@@ -1421,15 +1424,15 @@ def _extract_axis(data, axis=0, intersect=False):
     elif len(data) > 0:
         raw_lengths = []
         indexes = []
-
+        index = None
         have_raw_arrays = False
         have_frames = False
 
         for v in data.values():
             if isinstance(v, DataFrame):
                 have_frames = True
                 indexes.append(v._get_axis(axis))
-            else:
+            elif v is not None:
                 have_raw_arrays = True
                 raw_lengths.append(v.shape[axis])
 
@@ -1446,6 +1449,9 @@ def _extract_axis(data, axis=0, intersect=False):
             else:
                 index = Index(np.arange(lengths[0]))
 
+        if index is None:
+            index = Index([])
+
     return _ensure_index(index)
 
 

pandas/tests/test_panel.py

@@ -730,8 +730,9 @@ def test_ctor_dict(self):
 
         d = {'A' : itema, 'B' : itemb[5:]}
         d2 = {'A' : itema._series, 'B' : itemb[5:]._series}
-        d3 = {'A' : DataFrame(itema._series),
-              'B' : DataFrame(itemb[5:]._series)}
+        d3 = {'A' : None,
+              'B' : DataFrame(itemb[5:]._series),
+              'C' : DataFrame(itema._series)}
 
         wp = Panel.from_dict(d)
         wp2 = Panel.from_dict(d2) # nested Dict
@@ -748,6 +749,11 @@ def test_ctor_dict(self):
         assert_panel_equal(Panel(d2), Panel.from_dict(d2))
         assert_panel_equal(Panel(d3), Panel.from_dict(d3))
 
+        # a pathological case
+        d4 = { 'A' : None, 'B' : None }
+        wp4 = Panel.from_dict(d4)
+        assert_panel_equal(Panel(d4), Panel(items = ['A','B']))
+
         # cast
         dcasted = dict((k, v.reindex(wp.major_axis).fillna(0))
                        for k, v in d.iteritems())