__getattr__
这是python里的一个内建函数，当调用的属性或者方法不存在时，该方法会被调用
- 调用不存在的属性
class Student(object):
def __getattr__(self, attr):
if attr in ('name', 'age', 'score'):
print attr
else:
raise AttributeError('Unkonw attribute : %s' % attr)
In [8]: student = Student()
In [9]: student.name
name
In [10]: student.age
age
In [11]: student.call
AttributeError: Unkonw attribute : call
- 调用不存在的方法
class Student(object):
def __getattr__(self, attr):
def _func(*arg, **kwargs):
print arg, kwarg
if not attr.startswith('_'):
_func.func_name = attr
return _func
raise AttributeError('Unkonw attribute : %s' % attr)
In [22]: student = Student()
In [23]: student.name
Out[23]: <function __main__.name>
In [24]: student.name('a', 'b', c=1, d=2)
('a', 'b') {'c': 1, 'd': 2}
In [25]: student._age('a', 'b', c=1, d=2)
AttributeError: Unkonw attribute : _age
例一: 访问属性一样访问dict中的键值对
class Dict(dict):
def __init__(self, *args, **kwargs):
super(Dict, self).__init__(*args, **kwargs)
def __getattr__(self, name):
value = self[name]
if isinstance(value, dict):
value = Dict(value)
return value
In [27]: obj = Dict(student={'age': 18}, name='ZhangSan')
In [28]: obj
Out[28]: {'name': 'ZhangSan', 'student': {'age': 18}}
In [29]: obj.name
Out[29]: 'ZhangSan'
In [30]: obj.student
Out[30]: {'age': 18}
In [31]: obj.student.age
Out[31]: 18
