I propose something along these lines (patch to follow if the idea is sound):

class Differ:

    def __init__(self, linejunk=None, charjunk=None, sequence_matcher_factory=SequenceMatcher):

        # and so on

    def compare(self, a, b):

        cruncher = self.sequence_matcher_factory(self.linejunk, a, b)

        # and so on

The same general idea with unified_diff, ndiff, and context_diff

Basically, there are two obvious points of extension in difflib: The formatting of the output opcodes, and the method used to find sequences. The latter is not easily extended while reusing the former, and I'd like to change that. Note that I'm asking because I'd like to do the work, not because I want someone else to do it.

Is this a reasonable idea?