From ba0c4d7e2101a09bb97d7be08c698119c5d08c27 Mon Sep 17 00:00:00 2001
From: MohakGangwani <60480420+MohakGangwani@users.noreply.github.com>
Date: Mon, 1 Jun 2020 19:20:08 +0530
Subject: [PATCH] Update : In DataFrame Class, Columns should not contain
 duplicate values.

Also updated the Docstring.
---
 pandas/core/frame.py | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index dfc938918f03a..ce47314ad4328 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -357,6 +357,8 @@ class DataFrame(NDFrame):
     columns : Index or array-like
         Column labels to use for resulting frame. Will default to
         RangeIndex (0, 1, 2, ..., n) if no column labels are provided.
+        Columns Labels should not contain duplicate values, if column 
+        labels are provided.
     dtype : dtype, default None
         Data type to force. Only a single dtype is allowed. If None, infer.
     copy : bool, default False
@@ -442,6 +444,11 @@ def __init__(
             data = {}
         if dtype is not None:
             dtype = self._validate_dtype(dtype)
+            
+        #We need columns to have unique labels.
+        if columns != None:
+            if len(columns) != len(set(columns)):
+                raise Exception("Columns should not contain duplicate values.")
 
         if isinstance(data, DataFrame):
             data = data._mgr