3.3.5 Additional methods for emulation of sequence types
The following methods can be defined to further emulate sequence
objects. Immutable sequences methods should only define
__getslice__(); mutable sequences, should define all three
three methods.
Called to implement evaluation of self[i:j].
The returned object should be of the same type as self. Note
that missing i or j in the slice expression are replaced
by zero or sys.maxint, respectively, and no further
transformations on the indices is performed. The interpretation of
negative indices and indices larger than the length of the sequence is
up to the method.
Called to implement deletion of self[i:j].
Same notes for i and j as for __getslice__().
Notice that these methods are only invoked when a single slice with a
single colon is used. For slice operations involving extended slice
notation, __getitem__(), __setitem__()
or__delitem__() is called.
