monkey.py 文件源码

def patch_sys(stdin=True, stdout=True, stderr=True):
    """Patch sys.std[in,out,err] to use a cooperative IO via a threadpool.

    This is relatively dangerous and can have unintended consequences such as hanging
    the process or `misinterpreting control keys`_ when ``input`` and ``raw_input``
    are used.

    This method does nothing on Python 3. The Python 3 interpreter wants to flush
    the TextIOWrapper objects that make up stderr/stdout at shutdown time, but
    using a threadpool at that time leads to a hang.

    .. _`misinterpreting control keys`: https://github.com/gevent/gevent/issues/274
    """
    # test__issue6.py demonstrates the hang if these lines are removed;
    # strangely enough that test passes even without monkey-patching sys
    if PY3:
        return

    if stdin:
        _patch_sys_std('stdin')
    if stdout:
        _patch_sys_std('stdout')
    if stderr:
        _patch_sys_std('stderr')