I am doing a table join and would like to rename columns in the resulting table acs afterwards. So I set:

acs.columns = ["chr","start", "end", "rep1", "rep2"]

It allegedly works:

In [11]: acs.columns
Out[11]: ['chr', 'start', 'end', 'rep1', 'rep2']

But not really:

In [12]: acs.head()
Out[12]:
    chr  start    end  counts_x  counts_y
0  chr1  15765  17765         5         1
...