In [1]: from pandas import * In [2]: df = DataFrame({"A" : [1,2,3,4,5], "B": [3.1, 4, 5, 6, 7]}) In [3]: df[["A", "B"]]["A"] = 5 # no warning - bug?! In [4]: df Out[4]: A B 0 1 3.1 1 2 4.0 2 3 5.0 3 4 6.0 4 5 7.0 In [5]: df[["A"]]["A"] = 5 C:\Anaconda\Scripts\ipython-script.py:1: SettingWithCopyWarning: A value is trying to be set on a copy of a slice from a DataFrame. Try using .loc[row_indexer,col_indexer] = value instead See the the caveats in the documentation: http://pandas.pydata.org/pandas-docs/stable/indexing.html#indexing-view-versus-copy if __name__ == '__main__':