Start reading and writing on specific line on CSV with Python
===

I have a CSV file like this:
COL_A,COL_B
12345,A=1$B=2$C=3$

How do I read that file and wrote it back to a new file but just the second row (line)? 
I want the output file to contain:
12345,A=1$B=2$C=3$


Thanks!