使用logger.addHandler的logger.info / logger.error -如何拆分流？

Question

所以我把.info放在一个StringIO里，把.error放在另一个StringIO里。

我怎样才能阻止它们同时被放入其中呢？

前奏：

from __future__ import print_function

import logging

from io import IOBase
from sys import stdout
from platform import python_version_tuple

if python_version_tuple()[0] == '3':
    from IO import StringIO
else:
    try:
        from cStringIO import StringIO
    except ImportError:
        from StringIO import StringIO

代码：

# Some other file, like __init__.py
logging.basicConfig(
      format='%(asctime)s %(name)-12s %(levelname)-8s %(message)s', level='INFO')
handler = logging.root.handlers.pop()
assert logging.root.handlers == [], "root logging handlers aren't empty"
handler.stream.close()
handler.stream = stdout
logging.root.addHandler(handler)
# Some other file, like __init__.py

log = logging.getLogger(__name__)
stderr_stream = logging.StreamHandler(StringIO())
log.addHandler(stderr_stream)
log.setLevel(logging.ERROR)
print('log.level =', {logging.INFO: 'INFO',
                      logging.ERROR: 'ERROR'}[log.level])

stdout_stream = logging.StreamHandler(StringIO())
log.addHandler(stdout_stream)
log.setLevel(logging.INFO)
print('log.level =', {logging.INFO: 'INFO',
                      logging.ERROR: 'ERROR'}[log.level])

log.info('hello')
log.error('world')
print('stderr_stream =', stderr_stream.stream.getvalue())
print('stdout_stream =', stdout_stream.stream.getvalue())

http://ideone.com/Nj6Asz输出：

log.level = ERROR
log.level = INFO
2016-12-23 09:03:27,761 __main__     INFO     hello
2016-12-23 09:03:27,761 __main__     ERROR    world
stderr_stream = hello
world

stdout_stream = hello
world