general class functions

[Andrea Griffini]

On 1 Nov 2004 17:09:53 -0800, syd.diamond at gmail.com (syd) wrote:

>My question follows: is there a way I can make a general function for
>getting a subclass with my specific criteria?  For instance, can I
>pass in an equivalence test or something like that?  I have hundreds
>of variables like "nation", "continent", and so forth, and do want to
>write a separate "get______" function for each.

Adding the following method to Library

  def __getattr__(self,name):
    if name.startswith("get_"):
      attrname = name[4:]
      def filter(value):
        library=Library()
        for nation in self.list:
          if getattr(nation,attrname) == value:
            library.add(nation)
        return library
      return filter
    else:
      return self.__dict__[name]

you will be able to write

  L.get_continent('Europe').get_size('small')

because for anything starting with "get_..." will be
generated on the fly a filtering function that looks
for exact match of an attribute. No need for
getContinent, getSize, isContinent and isSize.

HTH
Andrea