Swap two stroke numbers in a [KanjiVG](https://github.com/KanjiVG/kanjivg) stroke order svg.

kvgswap.py

#! /usr/bin/env python2
# -*- coding: utf-8 ; mode: python -*-
# © Copyright 2013 ospalh@gmail.com
# License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html

import sys

__version__ = '0.0.1'

stroke_text_pattern = '>{0}</text>'


def swap_strokes(kanji, a, b):
    """Swap strokes in a kanjivg file"""
    # We do no checking at all. If something is wrong, just blow up.
    with open(kanji) as kf:
        lines = kf.readlines()
    num_a = -1
    num_b = -1
    line_a = u''
    line_b = u''
    line_a_pattern = stroke_text_pattern.format(a)
    line_b_pattern = stroke_text_pattern.format(b)
    for n, l in enumerate(lines):
        if line_a_pattern in l:
            num_a = n
            line_a = l
        if line_b_pattern in l:
            num_b = n
            line_b = l
    if num_a < 0 or num_b < 0:
        raise RuntimeError("Did not find both lines")
    lines[num_a] = line_b.replace(line_b_pattern, line_a_pattern)
    lines[num_b] = line_a.replace(line_a_pattern, line_b_pattern)
    with open(kanji, 'w') as kf:
        for l in lines:
            kf.write(l)


if __name__ == '__main__':
    helpmsg = u"""Usage: kvgswap FILE STROKE_A STROKE_B
Swaps strokes A and B in a kanjivg svg file.
"""
    if len(sys.argv) != 4:
        print helpmsg
        sys.exit(0)
    swap_strokes(sys.argv[1], sys.argv[2], sys.argv[3])