pandas dataframe remove constant column

Question

I have a dataframe that may or may not have columns that are the same value. For example

    row    A    B

    1      9    0

    2      7    0

    3      5    0

    4      2    0

I'd like to return just

   row    A  

   1      9    

   2      7    

   3      5    

   4      2

Is there a simple way to identify if any of these columns exist and then remove them?

Answer 1

I believe this option will be faster than the other answers here as it will traverse the data frame only once for the comparison and short-circuit if a non-unique value is found.

>>> df

   0  1  2

0  1  9  0

1  2  7  0

2  3  7  0

>>> df.loc[:, (df != df.iloc[0]).any()] 

   0  1

0  1  9

1  2  7

2  3  7

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