Use of lambda functions in OOP, any alternative?

Pablo incall at msn.com
Tue May 23 15:55:58 CEST 2006


Hello all, sorry if this is a faq...

Problem: The intended effect is to override the method 'getattr' in a
way that i dont need to override the property explicitly too.

class Base(object):
    def __init__(self, attr):
        self._attr = attr
    def getattr(self):
        return self._attr
    attr = property(fget=getattr)

class Derived(Base):
    def getattr(self):
        return 2*self._attr

if __name__ == "__main__":
    b = Base(4)
    d = Derived(4)
    print b.attr, d.attr

output>> 4 8 ... so this does not work as i would like it to.

First solution: This is not what i want.

class Derived(Base):
    def getattr(self):
        return 2*self._attr
    attr = property(fget=getattr)

Second solution: This is what i want, but...

class Base(object):
    def __init__(self, attr):
        self._attr = attr
    def getattr(self):
        return self._attr
    attr = property(fget=lambda self: self.getattr())

class Derived(Base):
    def getattr(self):
        return 2*self._attr

Question: Isn't there an *alternative* way to do it without the lambda
function?

Thanks in advance!




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