Create and use a temporary file.

gistfile1.txt

#!/usr/bin/env python3.4

import tempfile
from subprocess import call

with tempfile.NamedTemporaryFile() as f:
    for i in range(500):
        f.write(bytes("abcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghij\n", 'UTF-8'))
    f.flush()
    call(["cat", f.name])