Steven Bethard wrote: > Fuzzyman wrote: > >>>Steven Bethard wrote: > >>>> > >>>>So, one of my really common use cases that takes advantage of the > >>>>fact that default parameters are evaluated at function definition > >>>>time: > >>>> > >>>>def foo(bar, baz, matcher=re.compile(r'...')): > >>>> ... > >>>> text = matcher.sub(r'...', text) > >>>> ... > > Sure.. but you also gave an example of an alternative that was complex, > > Interesting. I would have thought that my example was pretty simple.
> Maybe it would be helpful to generalize it to: > > def foo(bar, baz, spam=badger(x, y, z)): > ... > > All it does is use a default value that was produced by a function call. > I'm surprised you haven't run into this situation before... > > Of course, what is complex or simple is a matter of personal opinion. I > use this pattern so often that it's quite simple to me, but I guess I > can understand that if you don't use such a pattern, it might seem > foreign to you. > > Steve Hello Steve, It wasn't that part of the example that I thought was over complex. (although it's not a 'pattern' I use often). You suggested that if we had dynamic evaluation of default values, you would have to replace it with : >>>> class foo(object): >>>> matcher=re.compile(r'...') >>>> def __new__(self, bar, baz, matcher=None): >>>> if matcher is None: >>>> matcher = self.matcher >>>> ... >>>> text = matcher.sub(r'...', text) >>>> ... Now that I thought was over complex... when all you wanted to do was put a constant into your default value ! Having said that I see Steve's point about not knowing the namespace when the function will be called. Regards, Fuzzy http://www.voidspace.org.uk/python/index.shtml -- http://mail.python.org/mailman/listinfo/python-list
