python自动格式化json文件的方法

class JsonFormatter:
  def __init__(self,intend=4,name=""):
    self.name=name
    self.intend=intend
    self.stack=[]
    self.obj=None
    self.source=self.get_source(name)
    self.prepare()
  @staticmethod
  def json_str(s):
    return '"'+s+'"'
  @staticmethod
  def get_source(name):
    with open(name,'r') as f:
      return ''.join(f.read().split())
  def prepare(self):
    try:
      self.obj=eval(self.source)
    except:
      raise Exception('Invalid json string!')
  def line_intend(self,level=0):
    return '\n'+' '*self.intend*level
  def parse_dict(self,obj=None,intend_level=0):
    self.stack.append(self.line_intend(intend_level)+'{')
    intend_level+=1
    for key,value in obj.items():
      key=self.json_str(str(key))
      self.stack.append(self.line_intend(intend_level)+key+':')
      self.parse(value,intend_level)
      self.stack.append(',')
    self.stack.append(self.line_intend(intend_level-1)+'}')
  def parse_list(self,obj=None,intend_level=0):
    self.stack.append(self.line_intend(intend_level)+'[')
    intend_level+=1
    for item in obj:
      self.parse(item,intend_level)
      self.stack.append(',')
    self.stack.append(self.line_intend(intend_level-1)+']')
  def parse(self,obj,intend_level=0):
    if obj is None:
      self.stack.append('null')
    elif obj is True:
      self.stack.append('true')
    elif obj is False:
      self.stack.append('false')
    elif isinstance(obj,(int,long,float)):
      self.stack.append(str(obj))
    elif isinstance(obj,str):
      self.stack.append(self.json_str(obj))
    elif isinstance(obj,(list,tuple)):
      self.parse_list(obj,intend_level)
    elif isinstance(obj,dict):
      self.parse_dict(obj,intend_level)
    else:
      raise Exception('Invalid json type %s!' % obj)
  def render(self):
    self.parse(self.obj,0)
    res_file='good'+self.name
    res=''.join(self.stack)
    with open(res_file,'w') as f:
      f.write(res)
    print res
if __name__=="__main__":
  jf=JsonFormatter(name="json.txt")
  jf.render()