[Python-Dev] Declaring setters with getters

[Guido van Rossum]

I've come up with a relatively unobtrusive pattern for defining
setters. Given the following definition:

def propset(prop):
    assert isinstance(prop, property)
    def helper(func):
        return property(prop.__get__, func, func, prop.__doc__)
    return helper

we can declare getters and setters as follows:

class C(object):

    _encoding = None

    @property
    def encoding(self):
        return self._encoding

    @propset(encoding)
    def encoding(self, value=None):
        if value is not None:
            unicode("0", value)  # Test it
        self._encoding = value

c = C()
print(c.encoding)
c.encoding = "ascii"
print(c.encoding)
try:
    c.encoding = "invalid"  # Fails
except:
    pass
print(c.encoding)

I'd like to make this a standard built-in, in the hope the debate on
how to declare settable properties.

I'd also like to change property so that the doc string defaults to
the doc string of the getter.

-- 
--Guido van Rossum (home page: http://www.python.org/~guido/)