blah.py

import ast

graph = {'A': set(['B', 'C']),
         'B': set(['A', 'D', 'E']),
         'C': set(['A', 'F']),
         'D': set(['B']),
         'E': set(['B', 'F']),
         'F': set(['C', 'E'])}

def dfs(graph, start):
    visited, stack = set(), [start]
    while stack:
        vertex = stack.pop()
        if vertex not in visited:
            visited.add(vertex)
            stack.extend(graph[vertex] - visited)
    return visited

dfs(graph, 'A') # {'E', 'D', 'F', 'A', 'C', 'B'}

mod = ast.parse("dale + 1")

stack = [mod]
jobs = []

while stack:
    node = stack.pop()
    jobs.append(node)
    for child_node in ast.iter_child_nodes(node):
        stack.append(child_node)

jobs = list(reversed(jobs))

done = {}
for node in jobs:
    ndict = {}
    done[node] = ndict
    for child_node in ast.iter_child_nodes(node):
        cdict = done[child_node]
        ndict[child_node] = cdict