[IronPython] DataBinding and INotifyPropertyChanged in IronPython

Lukas Cenovsky cenovsky at bakalari.cz
Wed Nov 11 15:12:39 CET 2009

__setattr__ is not clean and easy readable piece of code. That's why I 
dive into decorators and create a *notify_property*:

class notify_property(property):

    def __init__(self, getter):
        def newgetter(slf):
            #return None when the property does not exist yet
                return getter(slf)
            except AttributeError:
                return None
        super(notify_property, self).__init__(newgetter)

    def setter(self, setter):
        def newsetter(slf, newvalue):
            # do not change value if the new value is the same
            # trigger PropertyChanged event when value changes
            oldvalue = self.fget(slf)
            if oldvalue != newvalue:
                setter(slf, newvalue)
        return property(

The usage is the same as for @property - see details on my blog:

Unfortunately, this does not work in Silverlight - probably because such 
properties are not CLR fields. I'd like to find a way to make it work in 
Silverlight too.

-- Lukáš

Curt Hagenlocher wrote:
> Why don't you think that __setattr__ is a good approach? The 
> alternative (as shown in the linked Japanese-language blog) is to 
> implement setters for the properties you care about and to manually 
> trigger the event.
> 2009/11/6 Lukas Cenovsky <cenovsky at bakalari.cz 
> <mailto:cenovsky at bakalari.cz>>
>     Hi all,
>     I was looking for WPF data binding in IronPython and I have found
>     nice Japanese blog about it:
>     http://palepoli.skr.jp/wp/2009/06/28/wpf-listview-databinding-for-ironpython/
>     It links to
>     http://sdlsdk.codeplex.com/Thread/View.aspx?ThreadId=30322 that
>     should have more information about how to implement
>     INotifyPropertyChanged in IronPython which I am also interested
>     in. Unfortunately this page is no more available. Does the
>     guideline exist somewhere else? Thanks.
>     PS: I know about
>     http://lists.ironpython.com/pipermail/users-ironpython.com/2009-August/010938.html
>     but I don't think using __setattr__ is good approach. Also
>     implementing the PropertyChanged event is different on the blog.
>     --
>     -- Lukáš
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