How to get line count from Big file in Python?

You could execute a subprocess and run wc -l filename

import subprocessdef file_len(fname):    p = subprocess.Popen(['wc', '-l', fname], stdout=subprocess.PIPE,                                               stderr=subprocess.PIPE)    result, err = p.communicate()    if p.returncode != 0:        raise IOError(err)    return int(result.strip().split()[0])