Python是朵两生花 (__str__ __repe__ is) 讲的很清楚

In [1]: class Ctest(object):
   ...:     pass
   ...: 

In [2]: var = Ctest()

In [3]: var
Out[3]: <__main__.Ctest at 0x1619950>

In [4]: print var
<__main__.Ctest object at 0x1619950>

当仅仅定义__repr__时：

In [1]: class Ctest(object):
   ...:     def __repr__(self):
   ...:         return "Hi,I\‘m repr"
   ...:    

In [2]: var = Ctest()

In [3]: var
Out[3]: Hi,I\‘m repr

In [4]: print var
Hi,I\‘m repr


当仅仅定义__str__时：

In [5]: class Ctest(object):
   ...:     def __str__(self):
   ...:         return "Hi,I\‘m str"
   ...:    

In [6]: var = Ctest()

In [7]: var
Out[7]: <__main__.Ctest at 0x2938510>

In [8]: print var
Hi,I\‘m str


当2个都定义时：

In [12]: class Ctest(object):
    def __str__(self):
        return "Hi,I\‘m str"
    def __repr__(self):
        return "Hi,I\‘m repr"
   ....:    

In [13]: var = Ctest()

In [14]: var
Out[14]: Hi,I\‘m repr

In [15]: print var
Hi,I\‘m str

In [1]: Andy = [1,2,3]

In [2]: Bill = Andy

In [3]: Andy == Bill
Out[3]: True

In [4]: Andy is Bill
Out[4]: True

In [5]: Andy = [1,2,3]

In [6]: Bill = [1,2,3]

In [7]: Andy == Bill
Out[7]: True

In [8]: Andy is Bill
Out[8]: False