Le jeudi 07 septembre 2006 15:33, Steven Bethard a écrit : > Well, lambda's not going away[1],
Sure, they won't. > but there's no *need* for lambda here. > It could be written as:: Le jeudi 07 septembre 2006 17:16, George Sakkis a écrit : > Sure, it *could*; whether it *should* is a different issue. I can't > imagine a case for absolute *need* of lambda, but there are several > cases where it is probably the best way, such as the one of this > thread. I have no preferences here, I used lambdas because it's more compact but they have also their drawback, when the function get a little more complex the code is quickly confusing. The main advantage of the lambdas in this case is to not pollute the class namespace. Le jeudi 07 septembre 2006 23:48, Steven Bethard a écrit : > Try using one of the following recipies: > > http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/408713 > http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/442418 The code i wrote was to demonstrate late binding is usually not needed (and it's not the semantic of properties so it's a bit like "make Java in Python"). Only the second recipe has to do with it, but is not clean IMHO, it's unnecessary complicated and it introduce a extra level of indentation which is rather confusing, the 'self' variable in accessors is not what it seems to be. Moreover, it introduce a new semantic for a functionality which is already part of the language, what's the goal ? To lost python developers reading your code ? If you really want late binding, the first recipe may be a solution, but it should be both simpler and should not introduce a new semantic (the functions passed as strings is disappointing). I'd write it like this : class LateBindingProperty(property) : __doc__ = property.__dict__['__doc__'] # see bug #576990 def __init__(self, fget=None, fset=None, fdel=None, doc=None) : if fget : fget = lambda s, n=fget.__name__ : getattr(s, n)() if fset : fset = lambda s, v, n=fset.__name__ : getattr(s, n)(v) if fdel : fdel = lambda s, n=fdel.__name__ : getattr(s, n)() property.__init__(self, fget, fset, fdel, doc) In [4]: class A(object) : ...: def getx(self) : return self._x ...: def setx(self, v) : self._x = v ...: p=LateBindingProperty(getx, setx) ...: ...: In [5]: class B(A) : ...: def setx(self, v) : A.setx(self, 2*v) ...: ...: In [8]: a=A() In [9]: a.p = 5 In [10]: a.p Out[10]: 5 In [11]: a._x Out[11]: 5 In [12]: b=B() In [13]: b.p=5 In [14]: b.p Out[14]: 10 -- _____________ Maric Michaud _____________ Aristote - www.aristote.info 3 place des tapis 69004 Lyon Tel: +33 426 880 097 -- http://mail.python.org/mailman/listinfo/python-list
