python - Implementing Depth Limited Path Finding with Stack -

hey title says i'm trying implement depth limited search in python3 returns path given graph, start vertex , goal vertex. i'm struggling bit how enforce limit search. far have:

def dfs(g, v, goal, limit=-1):      sentinel = object()         visitedstack = [v]     path = ""      while visitedstack:         currentvertex = visitedstack.pop()              if g.getvertex(currentvertex) != none:             if g.getvertex(currentvertex).visited == false:                 path += currentvertex + ' -> '                  g.getvertex(currentvertex).hasbeenvisited()                  if currentvertex == goal:                      return path[:-3]                  elif currentvertex == sentinel:                     limit += 1                  elif limit != 0:                     limit -= 1                     visitedstack.append(sentinel)                     visitedstack.extend(g.getvertex(currentvertex).getconnections())        return "depth limit reached" 

edit: changed of code check visited vertices. after edit search getting returned doesn't work sometimes. example, i'll set depth limit 3, have path of 4 or 5 getting returned. other times i'll set limit 7 , have "limit reached" returned. note: smallest path 3

when search goes deeper level, push sentinel onto stack , decrement limit. when pop sentinel off stack increment level.

def dfs_limit(g, start, goal, limit=-1):     '''     perform depth first search of graph g.     if limit >= 0, maximum depth of search.     '''     sentinel = object()     visitedstack = [start]     path = []      while visitedstack:         currentvertex = visitedstack.pop()          if currentvertex == goal:              path.append(currentvertex)             return ' -> '.join(path)          elif currentvertex == sentinel:             #finished level; go 1 level             limit += 1             path.pop()          elif limit != 0:             # go 1 level deeper, push sentinel             limit -= 1             path.append(currentvertex)             visitedstack.append(sentinel)             visitedstack.extend(g.getvertex(currentvertex).getconnections()) 

if there loops or multiple routes through graph, need keep track of nodes have been visited don't duplicate work or in endless loop.