python - 具有多个值的属性 setter

Question

我有一个属性 setter ，它通过获取两个字符串并对其进行散列来生成一个唯一的 ID:

@id.setter
def id(self,value1,value2):
    self._id = sha512(value1+value2)

我有两个问题:

1. 是否允许(考虑良好的 Python 编码实践)以这种方式编码
2. 如何将两个值传递给 setter ？

Answer 1

How do I pass two values to the setter?

你可以传递一个 iterable(tuple, list) 给 setter，例如:

class A(object):
    def __init__(self, val):
        self.idx = val

    @property    
    def idx(self):
        return self._idx

    @idx.setter
    def idx(self, val):
        try:
            value1, value2 = val
        except ValueError:
            raise ValueError("Pass an iterable with two items")
        else:
            """ This will run only if no exception was raised """
            self._idx = sha512(value1+value2)

演示:

>>> a = A(['foo', 'bar'])     #pass a list
>>> b = A(('spam', 'eggs'))   #pass a tuple
>>> a.idx
<sha512 HASH object @ 0xa57e688>
>>> a.idx = ('python', 'org')  #works
>>> b.idx = ('python',)         #fails
Traceback (most recent call last):
    ...
    raise ValueError("Pass an iterable with two items")
ValueError: Pass an iterable with two items