Python内置函数(25)——getattr

英文文档：

getattr(object, name[, default])

Return the value of the named attribute of object. name must be a string. If the string is the name of one of the object’s attributes, the result is the value of that attribute. For example, getattr(x, 'foobar') is equivalent to x.foobar. If the named attribute does not exist, default is returned if provided, otherwise AttributeError is raised.

说明：

　　

　　1. 函数功能是从对象object中获取名称为name的属性，等效与调用object.name。

#定义类Student
>>> class Student:
    def __init__(self,name):
        self.name = name

>>> s = Stduent('Aim')
>>> getattr(s,'name') #等效于调用s.name
'Aim'
>>> s.name
'Aim'

　　2. 函数第三个参数default为可选参数，如果object中含义name属性，则返回name属性的值，如果没有name属性，则返回default值，如果default未传入值，则报错。

#定义类Student
>>> class Student:
    def __init__(self,name):
        self.name = name

>>> getattr(s,'name') #存在属性name
'Aim'

>>> getattr(s,'age',6) #不存在属性age，但提供了默认值，返回默认值
6

>>> getattr(s,'age') #不存在属性age，未提供默认值，调用报错
Traceback (most recent call last):
  File "<pyshell#17>", line 1, in <module>
    getattr(s,'age')
AttributeError: 'Stduent' object has no attribute 'age'