Python with PAGER

# Copyright (c) 2014 yuzurihara. All rights reserved.
# Released under the BSD 3-Clause License.
# http://opensource.org/licenses/BSD-3-Clause

import os
import sys
import subprocess
import atexit


def with_pager(func, *args, **kwargs):
  pager = os.getenv('PAGER', '/usr/bin/less')
  p2 = None
  stdout_save = sys.stdout
  def on_exit():
    if p2:
      p2.stdin.close()
      p2.wait()
    sys.stdout = stdout_save

  if pager and os.isatty(sys.stdout.fileno()):
    p2 = subprocess.Popen(
      pager, shell=True,
      stdin=subprocess.PIPE,
      universal_newlines=True)
    if p2.poll() is None:
      sys.stdout = p2.stdin
      atexit.register(on_exit)
    else: # Popen() failed.
      p2 = None
  try:
    retval = func(*args, **kwargs)
  finally:
    on_exit()
    atexit.unregister(on_exit)
  return retval