Pasted from IPython

file1.py

class Node:
    def __init__(self, data, children=None):
        self.data = data
        self.children = children or []
    def find(self, data):
        for i in self.descendants():
            if i.data == data:
                return i
    def descendants(self):
        yield self
        for i in self.children:
            yield from i.descendants()
    def __repr__(self):
        return "Node({!r})".format(self.data)
    def __iter__(self):
        yield from self.children