I wonder if anyone else out there in subscriber-world has Python Programming for Biology, by Stevens and Boucher. I'm enjoying it and learning a lot. PDB files... On page 75 this is given as the wrong way to pass a function for which you wish to set up some default parameters: def jobFunc(arg1, errorFunc('Warning', color='Red')) # Wrong I agree that's wrong because we don't want to be calling the function it this time merely passing it in as an object still uncalled, arguments pre-set. This errorFunc collapses to an object, gets evaluated prematurely. But then the "right way" (same page) is given as: def jobFunc(arg1, lambda: errorFunc('Warning', color="red')): I'd say that's wrong too as we've not bound this function to a name, so how in the function body is errorFunc to be triggered? No object is queued. I'd go with: def jobFunc(arg1, to_do = lambda x='Warning', color='red': errorFunc(x, color)): which gives the caller a way to override the defaults and not use errorFunc at all maybe. Otherwise, if the defaults are acceptable, just call to_do() in the body, with no args, and all will be well. Another pattern: def jobFunc(arg1, message = 'Warning', color='red'): # ... try: # etc. -- whatever it is that might not work pass except: errorFunc(message, color) That's assuming errorFunc is always appropriate and we're only concerned to maybe override its default arguments. That could work too. Kirby