def safe_walk(top, topdown=True, onerror=None, followlinks=True, _seen=None):
    islink, join, isdir = os.path.islink, os.path.join, os.path.isdir
    if _seen is None:
        _seen = set()

    # We may not have read permission for top, in which case we can't
    # get a list of the files the directory contains.  os.path.walk
    # always suppressed the exception then, rather than blow up for a
    # minor reason when (say) a thousand readable directories are still
    # left to visit.  That logic is copied here.
    try:
        # Note that listdir and error are globals in this module due
        # to earlier import-*.
        names = os.listdir(top)
    except os.error as err:
        if onerror is not None:
            onerror(err)
        return

    if followlinks:
        status = os.stat(top)
        # st_ino is always 0 on some filesystems (FAT, NTFS); ignore them
        if status.st_ino != 0:
            node = (status.st_dev, status.st_ino)
            if node in _seen:
                return
            _seen.add(node)

    dirs, nondirs = [], []
    for name in names:
        full_path = join(top, name)
        if isdir(full_path):
            dirs.append(name)
        else:
            nondirs.append(name)

    if topdown:
        yield top, dirs, nondirs
    for name in dirs:
        new_path = join(top, name)
        if followlinks or not islink(new_path):
            for x in safe_walk(new_path, topdown, onerror, followlinks, _seen):
                yield x
    if not topdown:
        yield top, dirs, nondirs
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dataset/ETHPy150Open saltstack/salt/salt/utils/__init__.py/safe_walk--crossover with--dataset/ETHPy150Open kdart/pycopia/QA/pycopia/terminal.py/Screen.erase_down