Copy the last three lines of a text file in python?

Question

I\'m new to python and the way it handles variables and arrays of variables in lists is quite alien to me. I would normally read a text file into a vector and then copy the

Answer 1

To get the last three lines of a file efficiently, use deque:

from collections import deque

with open('somefile') as fin:
    last3 = deque(fin, 3)

This saves reading the whole file into memory to slice off what you didn't actually want.

To reflect your comment - your complete code would be:

from collections import deque

with open('somefile') as fin, open('outputfile', 'w') as fout:
    fout.writelines(deque(fin, 3))