From bd45d391bce7fa2310c7dbe4646d4b1666783332 Mon Sep 17 00:00:00 2001
From: y-p <yoval@gmx.com>
Date: Sun, 11 Nov 2012 02:43:59 +0200
Subject: [PATCH] ENH: warn user when invoking to_dict() on df with non-unique
 columns

---
 pandas/core/frame.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index e4e9705e562d0..05d3713375481 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -837,6 +837,10 @@ def to_dict(self, outtype='dict'):
         -------
         result : dict like {column -> {index -> value}}
         """
+        import warnings
+        if not self.columns.is_unique:
+            warnings.warn("DataFrame columns are not unique, some "
+                          "columns will be omitted.",UserWarning)
         if outtype.lower().startswith('d'):
             return dict((k, v.to_dict()) for k, v in self.iteritems())
         elif outtype.lower().startswith('l'):