[IronPython] OnVarChanged

[John Mancine]

Shri,

Thanks for the advice, but I actually noticed that when I do..

pyEngine.Execute("a=1"), I do not in fact hit ModuleScope.SetGlobal(), but I
do however hit ModuleScope.SetLocal().

Care to shed some light on this? I am a bit lost as to what IronPython means
by 'local' and 'global' as it seems like they are very close to the same
thing in the sense that I can do engine.SetGlobal("a", 1) or
engine.Execute("a=1") and basically do the same thing but one goes through
SetGlobal() and one goes through SetLocal().

Take care,
John

> -----Original Message-----
> From: users-bounces at lists.ironpython.com [mailto:users-
> bounces at lists.ironpython.com] On Behalf Of Shri Borde
> Sent: Wednesday, June 21, 2006 2:00 PM
> To: Discussion of IronPython
> Subject: Re: [IronPython] OnVarChanged
> 
> You should be able to declare a type that inherits from ModuleScope, and
> override ModuleScope.Get/SetGlobal. That should be the hook you need. Then
> you can use engine.Execute("a=1", myCustomModuleScope).
> 
> Do you want to help develop Dynamic languages on CLR?
> (http://members.microsoft.com/careers/search/details.aspx?JobID=6D4754DE-
> 11F0-45DF-8B78-DC1B43134038)
> 
> -----Original Message-----
> From: users-bounces at lists.ironpython.com [mailto:users-
> bounces at lists.ironpython.com] On Behalf Of John Mancine
> Sent: Tuesday, June 20, 2006 11:05 AM
> To: 'Discussion of IronPython'
> Subject: Re: [IronPython] OnVarChanged
> 
> Thanks for the info.
> 
> I think I have found what I was looking for now. Basically, this is the
> earliest breakpoint that I hit after returning from the [Lightweight
> Function] on the call stack after engine.Execute("a=1") is called.
> 
> IronPython.Runtime.ModuleScope.SetLocal(SymbolId symbol, object value)
> 
> Sure looks promising at least. The symbol is 'a' and the value is '1'.
> 
> I also found a IronPython.Runtime.Operations.Ups.MakeClass() call which
> should be helpful for hooking into class declarations.
> 
> > -----Original Message-----
> > From: users-bounces at lists.ironpython.com [mailto:users-
> > bounces at lists.ironpython.com] On Behalf Of Michael Foord
> > Sent: Tuesday, June 20, 2006 11:59 AM
> > To: Discussion of IronPython
> > Subject: Re: [IronPython] OnVarChanged
> >
> > John Mancine wrote:
> > > I realize this is likely woefully naïve but I thought I'd ask anyhow.
> > >
> > > I have a very specific case in my project where I would really like to
> > know
> > > when a variable inside IronPython changes. Basically when I do this:
> > >
> > > pythonEngine.Execute("a = 3"); // Or something more complex that ends
> up
> > > changing global var 'a'
> > >
> > > I am looking for a way to be notified when 'a' has been assigned to a
> > new
> > > value. This seems to be pretty simple for the Set/GetGlobal() calls
> but
> > what
> > > about code that is inside of the Execute() block? Where could I look
> at
> > > adding some code myself such that I can add these hooks? I have dug
> > through
> > > some of the code to find a place to add a hook but I couldn't seem to
> > find
> > > anything clear cut.
> > >
> > > Again, I realize this is pretty simplistic and also painfully slow for
> > any
> > > moderate scripting but I have a very specific case where I would like
> > some
> > > widgets in C# to respond to when a variable has changed. (The
> > watchwindow in
> > > visual studio would be a good parallel of what I'm needing to do --
> ie.
> > show
> > > a new value has been set for a particular value you are watching).
> > >
> > >
> > Hello John,
> >
> > I may be off beam here (I'm no C# expert and know little about the
> > IronPython internals) but it sounds like what you want to do is a bit at
> > conflict with the way Python works.
> >
> > Python doesn't have variables by value as such, it has names and
> objects.
> >
> > In your example, 'a' isn't an object, it's a name bound to an object.
> >
> > When you do :
> >
> > a = 1
> > a = 2
> >
> > it's not that the value of a changes, instead the name is rebound to a
> > different object. Tracking changes to a mutable object is one thing, but
> > tracking name binding is a different thing altogether.
> >
> > Perhaps you could replace the ``__dict__`` attribute of a module (where
> > names are stored) with a custom 'dictionary-like' object, that calls a
> > callback when assignments are made ? A better approach would be to use a
> > value on an object (instead of a local variable), and you can get that
> > object to perform a callback when changes are made.
> >
> > All the best,
> >
> > Fuzzyman
> > http://www.voidspace.org.uk/python/index.shtml
> >
> > > Thanks!
> > > John
> > >
> > > _______________________________________________
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> > >
> > >
> >
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