在函数上定义 __getattr__ 和 __getitem__ 没有效果

免责声明这只是元编程的练习，没有实际意义 目的。

我已分配__getitem__ and __getattr__函数对象上的方法，但是 没有效果...

def foo():
  print "foo!"

foo.__getitem__ = lambda name: name
foo.__getattr__ = lambda name: name
foo.baz = 'baz'

健全性检查我们can为函数分配属性：

>>> foo.baz
'baz'

整洁的。那些“魔术师”又如何呢？

>>> foo.bar
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'function' object has no attribute 'bar'

>>> foo['foo']
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'function' object is not subscriptable

>>> getattr(foo, 'bar')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'function' object has no attribute 'bar'

函数对象上是否有可能有一个“神奇的吸气剂”？

没有！分配__getitem__到一个实例不起作用any对象类型：

>>> class A(object):
...   pass
...
>>> a = A()
>>> a.__getattr__ = lambda name: name
>>> a.foo
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'A' object has no attribute 'foo'

And你无法定义__getattr__关于内置函数类型：

>>> import types
>>> types.FunctionType.__getitem__ = lambda name: name
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: can't set attributes of built-in/extension type 'function'

And