#coding=utf-8 
def pretty_dict(obj, indent=' '): 
 def _pretty(obj, indent): 
  for i, tup in enumerate(obj.items()): 
   k, v = tup 
   #如果是字符串则拼上"" 
   if isinstance(k, basestring): k = '"%s"'% k 
   if isinstance(v, basestring): v = '"%s"'% v 
   #如果是字典则递归 
   if isinstance(v, dict): 
    v = ''.join(_pretty(v, indent + ' '* len(str(k) + ': {')))#计算下一层的indent 
   #case,根据(k,v)对在哪个位置确定拼接什么 
   if i == 0:#开头,拼左花括号 
    if len(obj) == 1: 
     yield '{%s: %s}'% (k, v) 
    else: 
     yield '{%s: %s,\n'% (k, v) 
   elif i == len(obj) - 1:#结尾,拼右花括号 
    yield '%s%s: %s}'% (indent, k, v) 
   else:#中间 
    yield '%s%s: %s,\n'% (indent, k, v) 
 print ''.join(_pretty(obj, indent)) 
 
d = { "root": { "folder2": { "item2": None, "item1": None }, "folder1": { "subfolder1": { "item2": None, "item1": None }, "subfolder2": { "item3": None } } } } 
pretty_dict(d)