Best way to reverse lines in a csv file python

I want to know the best way to reverse the lines of a big csv file (+50000 lines) in python 2.7 and rewrite it, avoiding the first line.

input:
A;B;C
1;2;3
4;5;6

output
A;B;C
4;5;6
1;2;3

I need to know how to do it in a efficient way in python 2.7.

Thank you guys,

menchopez