30-Python内置方法之__str__和__repr__

定义一个类，然后实例化，观察打印结果：

>>> class Person(object):
...     def __init__(self, name, age):
...         self.name = name
...         self.age = age
...         
>>> p = Person("druid", 18)
>>> p
<Person object at 0x11044b160>  # 直接调用对象打印的是内存地址
>>> print(p)
<Person object at 0x11044b160>  # 用print打印仍然是内存地址

在类中增加__str__方法，观察打印结果：

>>> class Person(object):
...     def __init__(self, name, age):
...         self.name = name
...         self.age = age
... 
...     def __str__(self):
...         return "{}-{}".format(self.name, self.age)
...     
>>> p1 = Person("druid", 18)
>>> p1
<Person object at 0x1105899e8>  # 直接调用对象打印的是内存地址
>>> print(p1)
druid-18  # 用print打印的是__str__返回的string

在类中增加__repr__方法，观察打印结果：

>>> class Person(object):
...     def __init__(self, name, age):
...         self.name = name
...         self.age = age
... 
...     def __repr__(self):
...         return "{}-{}".format(self.name, self.age)
...     
>>> p2 = Person("druid", 18)
>>> p2
druid-18  # 直接调用对象打印的是__repr__返回的string
>>> print(p2)
druid-18  # 用print打印仍然是__repr__返回的string