algebra.py 文件源码

def _traverseAgg(e, visitor=lambda n, v: None):
    """
    Traverse a parse-tree, visit each node

    if visit functions return a value, replace current node
    """

    res = []

    if isinstance(e, (list, ParseResults, tuple)):
        res = [_traverseAgg(x, visitor) for x in e]

    elif isinstance(e, CompValue):
        for k, val in e.iteritems():
            if val != None:
                res.append(_traverseAgg(val, visitor))

    return visitor(e, res)