class Test(object):
  def __init__(self, value='hello, world!'):
    self.data = value

> t = Test()
> t
<__main__.Test at 0x7fa91c307190>
> print t
<__main__.Test object at 0x7fa91c307190>

# 重构__repr__
class TestRepr(Test):
  def __repr__(self):
    return 'TestRepr(%s)' % self.data

> tr = TestRepr()
> tr        直接终端显示，不print就是面向程序员
TestRepr(hello, world!)
> print tr     print是面向程序员
TestRepr(hello, world!)

# 重构__str__
calss TestStr(Test):
  def __str__(self):
    return '[Value: %s]' % self.data

> ts = TestStr()
> ts
<__main__.TestStr at 0x7fa91c314e50>
> print ts
[Value: hello, world!]