Implementing UserList

This wrapper is similar to UserDict, except it applies to lists rather than dictionaries. Its main use is for creating a base class for list-like subclasses that allow for inheritance and method overriding or new methods. This allows for new functionality within lists.

Again, like UserDict, UserList has been largely superseded by the ability to subclass directly from list. But, again, it may be easier to use UserList than a list subclass. While UserList has the methods and capabilities of normal lists, it adds the data attribute to hold the underlying list object contents.

How to do it...

1. userlist_import.py shows how to use UserList as a superclass for a new list-like object. In this case, we are going to create a class that allows a list to be added by simply assigning values to it, rather than having to call the append() function:

• • First, in line 11, UserList must be imported from the collections module.
  • Next, the ExtendList class is created in line 12 as a subclass of...