Python difflib: highlighting differences inline?

Question

When comparing similar lines, I want to highlight the differences on the same line:

a) lorem ipsum dolor sit amet
b) lorem foo ipsum dolor amet

lorem 

        

Answer 1

Here's an inline differ inspired by @tzot's answer above (also Python 3 compatible):

def inline_diff(a, b):
    import difflib
    matcher = difflib.SequenceMatcher(None, a, b)
    def process_tag(tag, i1, i2, j1, j2):
        if tag == 'replace':
            return '{' + matcher.a[i1:i2] + ' -> ' + matcher.b[j1:j2] + '}'
        if tag == 'delete':
            return '{- ' + matcher.a[i1:i2] + '}'
        if tag == 'equal':
            return matcher.a[i1:i2]
        if tag == 'insert':
            return '{+ ' + matcher.b[j1:j2] + '}'
        assert False, "Unknown tag %r"%tag
    return ''.join(process_tag(*t) for t in matcher.get_opcodes())

It's not perfect, for example, it would be nice to expand 'replace' opcodes to recognize the full word replaced instead of just the few different letters, but it's a good place to start.

Sample output:

>>> a='Lorem ipsum dolor sit amet consectetur adipiscing'
>>> b='Lorem bananas ipsum cabbage sit amet adipiscing'
>>> print(inline_diff(a, b))
Lorem{+  bananas} ipsum {dolor -> cabbage} sit amet{-  consectetur} adipiscing