Class Collection

recipes/Python/107027_Simple_Collection_class/recipe-107027.py:5–25

Collections group objects together and forward attribute lookups. At least this is the Collection I remember from LYMB (an interpreted OO language developed by Bill Lorensen et al at GE CRD), which almost certainly got it from Smalltalk.

import UserList

class Collection(UserList.UserList):
    """Collections group objects together and forward attribute lookups.

    At least this is the Collection I remember from LYMB (an interpreted OO
    language developed by Bill Lorensen et al at GE CRD), which almost
    certainly got it from Smalltalk.
    """

    def get(self, attr):
        """return a list of attributes from ourselves.

        note that an object in the collection is not required to have 'attr',
        so the result may be shorter than the collection itself."""
        return Collection([getattr(x, attr) for x in self if hasattr(x, attr)])

    def call(self, attr, *args, **kwds):
        """return the result of calling 'attr' for each of our elements"""
        attrs = self.get(attr)
        return Collection([x(*args, **kwds)
                             for x in attrs
                               if callable(x)])

if __name__ == "__main__":
    import time