Tests make use of [[https://docs.python.org/3/library/timeit.html|timeit]] to ensure we are only measuring ''print()'' and ''write()''. ((//Not// the overhead of loading data into memory))

<file python print.py>
import timeit
import sys

setup = """
from sys import stdin

num_lines = int(input())
lines = stdin.readlines()


def myFun(stuff):
    for line in stuff:
        print(line)
"""

print(timeit.timeit("myFun(lines)", number=5, setup=setup), file=sys.stderr)


</file>

<file python write.py>

import timeit
import sys

setup = """
from sys import stdin, stdout

num_lines = int(input())

lines = stdin.readlines()

def myFun(stuff):
    for line in stuff:
        stdout.write(line)
"""

print(timeit.timeit("myFun(lines)",number=5,setup=setup), file=sys.stderr)
</file>


<file python read_test.py>
from sys import argv
from random import *
from string import *

for i in range(int(argv[1])):
    print(''.join(choice(ascii_lowercase + ' ') for _ in range(int(argv[2]))))
</file>


((''python3 read_test.py lines length > out.txt'', where ''lines'' is the number of lines and ''length'' is the number of characters per line.))