stream.py 文件源码

def redirect_stdout_to(stream_with_fd):
    if stream_with_fd is None:
        # no redirect when stream is 'None'
        yield
    else:
        # do not redirect, if streams do not have file descriptors!
        try:
            _sys_stdout_fileno = sys.stdout.fileno()
            _out_stream_fileno = stream_with_fd.fileno()
        except:
            yield
        else:
            # save the old stdout stream
            old_out_stream = os.dup(sys.stdout.fileno())
            os.dup2(stream_with_fd.fileno(), sys.stdout.fileno())

            # if all OK, yield back to the caller, catching exceptions
            try:
                yield
            finally:
                # restore the previous output stream
                os.dup2(old_out_stream, sys.stdout.fileno())
                os.close(old_out_stream)