listCtrl.SetStringItem() always seems to return '1'. Not sure if this is meant to represent "True" for a successful addition to the list? It appears that SetStringItem is a wxPython specific function, so I can't find any details about what it's supposed to return in the wx module docs.
I think I've found a solution though. I'm using a lambda on my binding function and passing it the python data object that I want to modify.
So now I have "list_control.Bind(wx.EVT_LIST_END_LABEL_EDIT, lambda event: self.OnEditVector(event,node))", where "node" is the data object I'm trying to modify.
and a relatively simple event handling function:
def OnEditVector(self,event,node):
index = event.GetColumn()
value = event.GetText()
node.data[index] = float(value)