def open_logfile(filename, mode='a'):
    """Open the named log file in append mode.

    If the file already exists, a separator will also be printed to
    the file to separate past activity from current activity.
    """
    filename = os.path.expanduser(filename)
    filename = os.path.abspath(filename)
    dirname = os.path.dirname(filename)
    if not os.path.exists(dirname):
        os.makedirs(dirname)
    exists = os.path.exists(filename)

    log_fp = open(filename, mode)
    if exists:
        log_fp.write(('-'*60) % '%s\n')
        log_fp.write('%s run on %s\n' % (sys.argv[0], time.strftime('%c')))
    return log_fp
dataset/ETHPy150Open cloudaice/simple-data/misc/virtenv/lib/python2.7/site-packages/pip-1.2.1-py2.7.egg/pip/basecommand.py/open_logfile/swapped operands of `%`