BUG: raise more helpful exception when passing empty list to MultiIndex.from_tuples

Author: wesm

pandas/core/index.py

@@ -999,6 +999,8 @@ def from_tuples(cls, tuples, sortorder=None, names=None):
         -------
         index : MultiIndex
         """
+        if len(tuples) == 0:
+            raise Exception('Cannot infer number of levels from empty list')
         arrays = zip(*tuples)
         return MultiIndex.from_arrays(arrays, sortorder=sortorder,
                                       names=names)

pandas/tests/test_index.py

@@ -922,6 +922,9 @@ def test_diff(self):
         result = self.index - self.index.sortlevel(1)[0]
         self.assert_(len(result) == 0)
 
+    def test_from_tuples(self):
+        self.assertRaises(Exception, MultiIndex.from_tuples, [])
+
     def test_argsort(self):
         result = self.index.argsort()
         expected = self.index.get_tuple_index().argsort()