Comment attribuer un nouvel attribut de classe via __dict__ en python?

Question

Je veux attribuer un attribut de classe via un objet chaîne - mais comment?

Exemple:

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

Il y a une fonction builtin pour cela:

setattr(test, attr_name, 10) 

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

Exemple:

>>> 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