diff.py

#!/usr/bin/env python3

"""Produce visual, HTML diffs of two files"""

from argparse import ArgumentError, FileType
from difflib import HtmlDiff

def load(filename):
    with open(filename, mode='r') as f:
        for line in f:
            yield line

def junk(junk_chars):
    try:
        return lambda c: c in set(junk_chars)
    except:
        raise ArgumentError('invalid argument: {}'.format(junk_chars))

def main(filename1, filename2, **kwargs):
    differ = HtmlDiff(**kwargs)
    print(
        differ.make_file(
            filename1,
            filename2,
            fromdesc=filename1,
            todesc=filename2
        )
    )

if __name__ == '__main__':
    import argparse
    parser = argparse.ArgumentParser(
        formatter_class=argparse.ArgumentDefaultsHelpFormatter,
        description=__doc__
    )
    parser.add_argument(
        'file1',
        type=FileType('r'),
        help='A file to diff against file2'
    )
    parser.add_argument(
        'file2',
        type=FileType('r'),
        help='A file to diff against file1'
    )
    parser.add_argument(
        '-w', '--wrapcolumn',
        type=int,
        default=None,
        help='Column number where lines are broken and wrapped'
    )
    parser.add_argument(
        '-j', '--junk',
        type=junk,
        default='',
        help=(
            'Characters to be considered junk; '
            'i.e., not considered part of the diff'
        )
    )
    args = parser.parse_args()
    main(
        args.file1,
        args.file2,
        wrapcolumn=args.wrapcolumn,
        charjunk=args.junk
    )