Read any number of files in parallel.

read_parallel.py

FIRST = 'path to first file'
SECOND = 'path to second file'


def main():
    with open(FIRST) as first, open(SECOND) as second:
        for line1, line2 in read_parallel(first, second):
            pass # process lines


def read_parallel(*files):
    lines = list(gather_lines(*files))
    while any(lines):
        yield lines
        lines = list(gather_lines(*files))


def gather_lines(*files):
    for f in files:
        yield f.readline()


if __name__ == '__main__':
    main()