Renaming columns in a Pandas dataframe with duplicate column names?

Question

I have a df X with columns with duplicate names:

In [77]: X_R
Out[77]: 
      dollars  dollars
   0   0.7085   0.5000

I want to rename it so that I have:

In [77]: X_R
Out[77]: 
       Retail   Cost
   0   0.7085   0.5000

Using the Pandas rename function does' work:

X_R.rename(index=str, columns={"dollars": "Retail", "dollars": "Cost"})

Just gives me two columns named Cost.

How can I rename the columns in this case?

Answer 1

Here is a dynamic solution:

In [59]: df
Out[59]:
   a  x  x  x  z
0  6  2  7  7  8
1  6  6  3  1  1
2  6  6  7  5  6
3  8  3  6  1  8
4  5  7  5  3  0

In [60]: d
Out[60]: {'x': ['x1', 'x2', 'x3']}

In [61]: df.rename(columns=lambda c: d[c].pop(0) if c in d.keys() else c)
Out[61]:
   a  x1  x2  x3  z
0  6   2   7   7  8
1  6   6   3   1  1
2  6   6   7   5  6
3  8   3   6   1  8
4  5   7   5   3  0