Pandas - Cannot sort by duplicate column

Question

When I sort one of my dataframes, e.g.:

my_df.sort(['column_A', 'column_B'])

I get:

ValueError: Cannot sort by duplicate column ['A', 'B']

The columns have different data and different names. Here is the full error:

/Users/josh/anaconda/envs/py27/lib/python2.7/site-packages/pandas/core/frame.pyc in sort(self, columns, column, axis, ascending, inplace)                
   2534             columns = column
   2535         return self.sort_index(by=columns, axis=axis, ascending=ascending,                                                                           
-> 2536                                inplace=inplace)
   2537 
   2538     def sort_index(self, axis=0, by=None, ascending=True, inplace=False,    


/Users/josh/anaconda/envs/py27/lib/python2.7/site-packages/pandas/core/frame.pyc in sort_index(self, axis, by, ascending, inplace, kind)                 
   2603                 if k.ndim == 2:
   2604                     raise ValueError('Cannot sort by duplicate column % s'                                                                            
-> 2605                                      % str(by))
   2606                 indexer = k.argsort(kind=kind)
   2607                 if isinstance(ascending, (tuple, list)):

ValueError: Cannot sort by duplicate column ['A', 'B']

Update:

Here is the dataframe:

> my_df.head()
                            db_pixel                                      db_advertiser-campaign
0                Schnucks - Rockford  GateHouse Media- Inc. Q1_2013--Katy's Pet Cemetary_1.13.14
1                 Speedway Auto Mall  GateHouse Media- Inc. Q1_2013--Katy's Pet Cemetary_1.13.14
2   Hagerstown Honda_Homepage_1.9.14  GateHouse Media- Inc. Q1_2013--Katy's Pet Cemetary_1.13.14
3                      Mitchell Gold  GateHouse Media- Inc. Q1_2013--Katy's Pet Cemetary_1.13.14
4  Gambino Realtors - PropelRETARGET  GateHouse Media- Inc. Q1_2013--Katy's Pet Cemetary_1.13.14

[5 rows x 2 columns]

Note that I am also having the error with the following command:

> my_df.head().sort(['db_pixel', 'db_advertiser-campaingn'])                                                               

Answer 1

I realized I was calling df.sort(columns=[my_columns]) instead of df.sort(columns=my_columns). In an effort to simplify the OP I didn't accurately write the exact call I was making. Sorry for the confusion