How to read in only every second line of file?

Question

I need to read in only every second line of a file (which is very big) so I don\'t want to use readlines(). I\'m unsure how to implement the iterator so any sug

Answer 1

You can use a custom iterator:

def iterate(pth):
    for i, line in enumerate(pth, 1):
        if not i % 2:
            yield line

Answer 2

Using itertools.islice:

import itertools

with open(pth_file) as f:
    for line in itertools.islice(f, 1, None, 2):
        # 1: from the second line ([1])
        # None: to the end
        # 2: step

        # Do something with the line