Merge pull request #3245 from jreback/GH3243

BUG: GH3243 accept list of DataFrames as constructor input

Author: jreback

pandas/core/common.py

@@ -1028,7 +1028,7 @@ def _possibly_convert_platform(values):
 
     if isinstance(values, (list,tuple)):
         values = lib.list_to_object_array(values)
-    if values.dtype == np.object_:
+    if getattr(values,'dtype',None) == np.object_:
         values = lib.maybe_convert_objects(values)
 
     return values

pandas/tests/test_frame.py

@@ -2040,6 +2040,15 @@ def test_constructor_dtype_list_data(self):
         self.assert_(df.ix[1, 0] is None)
         self.assert_(df.ix[0, 1] == '2')
 
+    def test_constructor_list_frames(self):
+
+        # GH 3243
+        result = DataFrame([DataFrame([])])
+        self.assert_(result.shape == (1,0))
+
+        result = DataFrame([DataFrame(dict(A = range(5)))])
+        self.assert_(type(result.iloc[0,0]) == DataFrame)
+
     def test_constructor_mixed_dtypes(self):
 
         def _make_mixed_dtypes_df(typ, ad = None):