# 例子在原来的基础上简化了一下，排除依赖和干扰，详细参见原项目
class UrlGenerator(object):
  def __init__(self, root_url):
    self.url = root_url

  def __getattr__(self, item):
    if item == 'get' or item == 'post':
      print self.url
    return UrlGenerator('{}/{}'.format(self.url, item))


url_gen = UrlGenerator('http://xxxx')
url_gen.users.show.get

>>> http://xxxx/users/show

class Test(object):
  def __init__(self,name):
    self.name = name
  def __getattr__(self, value):
    if value == 'address':
      return 'China'

if __name__=="__main__":
  test = Test('letian')
  print test.name
  print test.address
  test.address = 'Anhui'
  print test.address

letian
China
Anhui

class Test(object):
  def __init__(self,name):
    self.name = name
  def __getattr__(self, value):
    return len

if __name__=="__main__":
  test = Test('letian')
  print test.getlength('letian')

class Test(object):
  def __init__(self,name):
    self.name = name
  def __getattribute__(self, value):
    if value == 'address':
      return 'China'
    

if __name__=="__main__":
  test = Test('letian')
  print test.name
  print test.address
  test.address = 'Anhui'
  print test.address

None
China
China

class Test(object):
  def __init__(self, p):
    self.p = p

  def __getattr__(self, item):
    return 'default'

t = Test('p1')
print t.p
print t.p2

>>> p1
>>> default

class AboutAttr(object):
  def __init__(self, name):
    self.name = name

  def __getattribute__(self, item):
    try:
      return super(AboutAttr, self).__getattribute__(item)
    except KeyError:
      return 'default'

class AboutAttr(object):
  def __init__(self, name):
    self.name = name

  def __getattribute__(self, item):
    try:
      return super(AboutAttr, self).__getattribute__(item)
    except KeyError:
      return 'default'
    except AttributeError as ex:
      print ex

  def __getattr__(self, item):
    return 'default'

at = AboutAttr('test')
print at.name
print at.not_exised

>>>test
>>>'AboutAttr' object has no attribute 'not_exised'
>>>None