ENH: add keys() method to DataFrame, close #1240

Author: wesm

pandas/core/frame.py

@@ -530,6 +530,9 @@ def __iter__(self):
         """
         return iter(self.columns)
 
+    def keys(self):
+        return self.columns
+
     def iteritems(self):
         """Iterator over (column, series) pairs"""
         return ((k, self[k]) for k in self.columns)

pandas/tests/test_frame.py

@@ -1322,6 +1322,9 @@ def test_set_columns(self):
         self.assertRaises(Exception, setattr, self.mixed_frame, 'columns',
                           cols[::2])
 
+    def test_keys(self):
+        self.assert_(self.frame.keys() is self.frame.columns)
+
     def test_column_contains_typeerror(self):
         try:
             self.frame.columns in self.frame