Convert a pinyin string to bopomofo （Zhuyin)

bopomofo.py

# -*- coding: utf-8 -*-
#
# Copyright © 2012 Thomas TEMPÉ, <thomas.tempe@alysse.org>
# Copyright © 2014 Alex Griffin, <alex@alexjgriffin.com>
#
# DWTFYW license.
# Do what the fuck you want with this file.

import string

# early replacements
replacements = [
    (u"yu",   u"u:"),   (u"ü",    u"u:"),   (u"v", u"u:"),
    (u"yi",   u"i"),    (u"you",  u"ㄧㄡ"), (u"y", u"i"),
    (u"wu",   u"u"),    (u"wong", u"ㄨㄥ"), (u"w", u"u"),
]

table = [
    # special cases
    (u"ju",   u"ㄐㄩ"), (u"qu",   u"ㄑㄩ"), (u"xu",  u"ㄒㄩ"),
    (u"zhi",  u"ㄓ"),   (u"chi",  u"ㄔ"),   (u"shi", u"ㄕ"),   (u"ri",   u"ㄖ"),
    (u"zi",   u"ㄗ"),   (u"ci",   u"ㄘ"),   (u"si",  u"ㄙ"),
    (u"r5",   u"ㄦ"),

    # initials
    (u"b",    u"ㄅ"),   (u"p",    u"ㄆ"),   (u"m",   u"ㄇ"),   (u"f",    u"ㄈ"),
    (u"d",    u"ㄉ"),   (u"t",    u"ㄊ"),   (u"n",   u"ㄋ"),   (u"l",    u"ㄌ"),
    (u"g",    u"ㄍ"),   (u"k",    u"ㄎ"),   (u"h",   u"ㄏ"),
    (u"j",    u"ㄐ"),   (u"q",    u"ㄑ"),   (u"x",   u"ㄒ"),
    (u"zh",   u"ㄓ"),   (u"ch",   u"ㄔ"),   (u"sh",  u"ㄕ"),   (u"r",    u"ㄖ"),
    (u"z",    u"ㄗ"),   (u"c",    u"ㄘ"),   (u"s",   u"ㄙ"),

    # finals
    (u"i",    u"ㄧ"),   (u"u",    u"ㄨ"),   (u"u:",  u"ㄩ"),
    (u"a",    u"ㄚ"),   (u"o",    u"ㄛ"),   (u"e",   u"ㄜ"),   (u"ê",    u"ㄝ"),
    (u"ai",   u"ㄞ"),   (u"ei",   u"ㄟ"),   (u"ao",  u"ㄠ"),   (u"ou",   u"ㄡ"),
    (u"an",   u"ㄢ"),   (u"en",   u"ㄣ"),   (u"ang", u"ㄤ"),   (u"eng",  u"ㄥ"),
    (u"er",   u"ㄦ"),
    (u"ia",   u"ㄧㄚ"), (u"io",   u"ㄧㄛ"), (u"ie",  u"ㄧㄝ"), (u"iai",  u"ㄧㄞ"),
    (u"iao",  u"ㄧㄠ"), (u"iu",   u"ㄧㄡ"), (u"ian", u"ㄧㄢ"),
    (u"in",   u"ㄧㄣ"), (u"iang", u"ㄧㄤ"), (u"ing", u"ㄧㄥ"),
    (u"ua",   u"ㄨㄚ"), (u"uo",   u"ㄨㄛ"), (u"uai", u"ㄨㄞ"),
    (u"ui",   u"ㄨㄟ"), (u"uan",  u"ㄨㄢ"), (u"un",  u"ㄨㄣ"),
    (u"uang", u"ㄨㄤ"), (u"ong",  u"ㄨㄥ"),
    (u"u:e",  u"ㄩㄝ"), (u"u:an", u"ㄩㄢ"), (u"u:n", u"ㄩㄣ"), (u"iong", u"ㄩㄥ"),

    # tones
    (u"1",    u""),     (u"2",    u"ˊ"),
    (u"3",    u"ˇ"),    (u"4",    u"ˋ"),
    (u"5",    u"˙"),
]

table.sort(key=lambda pair: len(pair[0]), reverse=True)
replacements.extend(table)


def bopomofo(pinyin):
    '''Convert a pinyin string to Bopomofo
    The optional tone info must be given as a number suffix, eg: 'ni3'
    '''

    pinyin = pinyin.lower()
    for pair in replacements:
        pinyin = string.replace(pinyin, pair[0], pair[1])

    return pinyin


if __name__ == "__main__":
    import unittest

    bopomofo_tests = [
        # a few of these are extremely rare in usage
        (u"dong1 xi5", u"ㄉㄨㄥ ㄒㄧ˙"),
        (u"lai2",      u"ㄌㄞˊ"),
        (u"shui3",     u"ㄕㄨㄟˇ"),
        (u"de5",       u"ㄉㄜ˙"),
        (u"shi4",      u"ㄕˋ"),
        (u"zi3",       u"ㄗˇ"),
        (u"ri4",       u"ㄖˋ"),
        (u"ren2",      u"ㄖㄣˊ"),
        (u"er4",       u"ㄦˋ"),
        (u"r5",        u"ㄦ"),
        (u"qu3",       u"ㄑㄩˇ"),
        (u"xiong1",    u"ㄒㄩㄥ"),
        (u"yue4",      u"ㄩㄝˋ"),
        (u"yai2",      u"ㄧㄞˊ"),
        (u"yo1",       u"ㄧㄛ"),
        (u"yi1",       u"ㄧ"),
        (u"you3",      u"ㄧㄡˇ"),
        (u"wu3",       u"ㄨˇ"),
        (u"wong1",     u"ㄨㄥ"),
        (u"e2",        u"ㄜˊ"),
        (u"ê4",        u"ㄝˋ"),
    ]

    class BopomofoTest(unittest.TestCase):
        def test_bopomofo(self):
            for pair in bopomofo_tests:
                input = pair[0]
                out = pair[1]
                actual = bopomofo(pair[0])
                if actual != out:
                    raise RuntimeError("\"%s\": got %s, expected %s" % (input, actual, out))

    unittest.main()

Added support for tone mark.
If you want more similar code, please check out ttempe/Chinese-support-addon's Chinese/edit_functions.py.

Corrected an error where "sh" was processed as "s"+"h".
Corrected a misconception where "shi" was written "ㄕㄧ" instead of "ㄕ"
If you are familiar with Zhuyin yourself and find more problem, please give me feedback.

Taking Alex Griffin's version. Finally something more serious from an actual Bopomofo user... :)