如何通过 __dict__ 分配新的类属性？

Question

我想通过一个字符串对象来分配一个类属性——但是怎么做呢？

例子：

class test(object):
  pass

a = test()
test.value = 5
a.value
# -> 5
test.__dict__['value']
# -> 5

# BUT:
attr_name = 'next_value'

test.__dict__[attr_name] = 10
# -> 'dictproxy' object does not support item assignment

Answer 1

有一个内置函数：

setattr(test, attr_name, 10)

参考：http://docs.python.org/library/functions.html#setattr

例子：

>>> class a(object): pass
>>> a.__dict__['wut'] = 4
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'dictproxy' object does not support item assignment
>>> setattr(a, 'wut', 7)
>>> a.wut
7