Python: truncate a file to 100 lines or less

Question

I'm pretty new to Python - just wondering if there was a library function or easy way to truncate a file to the first 100 lines or less?

Answer 1

with open("my.file", "r+") as f:
    [f.readline() for x in range(100)]
    f.truncate()

EDIT A 5 % speed increase can be had by instead using the xrange iterator and not storing the entire list:

with open("my.file", "r+") as f:
    for x in xrange(100):
        f.readline()
    f.truncate()

Answer 2

Use one of the solutions here: Iterate over the lines of a string and just grab the first hundred, i.e.

import itertools
lines = itertools.islice(iter, 100)