compat.py 文件源码

def _get_text_writer(stream, errors):
        # In python3, all the sys.stdout/sys.stderr streams are in text
        # mode.  This means they expect unicode, and will encode the
        # unicode automatically before actually writing to stdout/stderr.
        # In python2, that's not the case.  In order to provide a consistent
        # interface, we can create a wrapper around sys.stdout that will take
        # unicode, and automatically encode it to the preferred encoding.
        # That way consumers can just call get_text_writer(stream) and write
        # unicode to the returned stream.  Note that get_text_writer
        # just returns the stream in the PY3 section above because python3
        # handles this.

        # We're going to use the preferred encoding, but in cases that there is
        # no preferred encoding we're going to fall back to assuming ASCII is
        # what we should use. This will currently break the use of
        # PYTHONIOENCODING, which would require checking stream.encoding first,
        # however, the existing behavior is to only use
        # locale.getpreferredencoding() and so in the hope of not breaking what
        # is currently working, we will continue to only use that.
        encoding = locale.getpreferredencoding()
        if encoding is None:
            encoding = "ascii"

        return codecs.getwriter(encoding)(stream, errors)