visitors.py 文件源码

def iterate(obj, opts):
    """traverse the given expression structure, returning an iterator.

    traversal is configured to be breadth-first.

    """
    # fasttrack for atomic elements like columns
    children = obj.get_children(**opts)
    if not children:
        return [obj]

    traversal = deque()
    stack = deque([obj])
    while stack:
        t = stack.popleft()
        traversal.append(t)
        for c in t.get_children(**opts):
            stack.append(c)
    return iter(traversal)