lambdas

[Craig Yoshioka]

I'm trying to write a class factory to create new classes dynamically at runtime from simple 'definition' files that happen to be written in python as well.  I'm using a class factory since I couldn't find a way to use properties with dynamically generated instances, for example:

I would prefer this, but it doesn't work:

class Status(object):
	pass

def makeStatus(object):
	def __init__(self,definitions):
		for key,function in definitions:
			setattr(self,key,property(function))

this works (and it's fine by me):

def makeStatus(definitions):
	class Status(object):
		pass
	for key,function in definitions:
		setattr(Status,key,property(function))
	return Status()

but I would also like the functions to only be evaluated when necessary since some may be costly, so I want to do the following:

def makeStatus(definitions):
	class Status(object):
		pass
	for key,function,data in definitions:
		setattr(Status,key,property(lambda x: function(data)))
	return Status()

but all my properties now act as if they were invoked with the same data even though each one should have been a new lambda function with it's own associated data.  It seems Python is 'optimizing'?  all the lambdas to the same object even though that's clearly not what I want to do.  Anyone have any suggestions as to:

1) why
2) what I should do
3) a better way in which to implement this pattern


Cheers!,
-Craig