sum2.py

def read_file_by_chunks(filename):
    chunk_size = 9+1
    with open(filename) as f:
        read_bytes = 0
        while True:
            chunk = f.read(chunk_size)
            chunk = chunk.strip()
            if not chunk:
                break
            if '\n' in chunk:
                index = chunk.index('\n')
            elif ' ' in chunk:
                index = chunk.index(' ')
            else:
                index = len(chunk)
            yield int(chunk[:index])
            read_bytes += index + 1
            f.seek(read_bytes)

def two_sum(filename):
    target_lst = []
    source_lst = []
    target = None
    comp = {}

    for num in read_file_by_chunks(filename):
        if target is None:
            target = num
        else:
            if num in comp:
                return 1
            comp[target - num] = True
    return 0


if __name__ == '__main__':
    result = two_sum("./input.txt")
    with open("./output.txt", "w+") as f:
        f.write(str(result))