DouKaku?

# encoding: utf-8
list = [ "abc\\def", "abc\\def\\gh", "abc\\def\\ij", "abc\\jk\\lm", "de" ]

def pathtree(lst):
  def maketree(l):
    s = [x for x in set([v[0] for v in l])]
    s.sort()
    return [[v, maketree([x[1:] for x in l if x[0]==v and len(x)>1])] for v in s]
  return ["ROOT", maketree([s.split("\\") for s in list])]

def printtree(tree):
  def printchild(tree, nest):
    for c in tree:
      if c==[]: continue
      print " "*nest*2 + "┗" + c[0]
      printchild(c[1], nest+1)
  print tree[0]
  printchild(tree[1], 0)

printtree(pathtree(list))