nbsplitter

A tool for splitting Japanese text into graphemes (i.e. the smallest unit of written text that preserves pronunciation).

Context

Splitting Japanese graphemes as defined here isn't exactly a straightforward task. Ignoring kana (since each character neatly maps to a single pronunciation), there are quite a few nuances to consider: each individual kanji has several possible readings, certain groupings of kanji must be considered unique graphemes because their pronunciations aren't obtainable by merely combining individual kanji readings, and so on. This package elegantly handles the vast majority of these exceptions under the hood and exposes a single interface for splitting graphemes as desired.

Usage

>>> from nbsplitter import split_graphemes
>>> graphemes = split_graphemes("東大和市")
>>> print(graphemes.surface())
['東', '大和', '市']
>>> print(graphemes.reading_form())
['ヒガシ', 'ヤマト', 'シ']

Known Limitations

Inability to differentiate between rendaku and arbitrary unvoiced-to-voiced consonant changes

As noted in the documentation below, the splitter algorithm cannot definitively distinguish between examples of true rendaku and multi-kanji graphemes whose second component appears to be read as the voiced equivalent of one of its standalone readings. For example, consider the output below:

graphemes = split_graphemes("富士", split_rendaku=True)
print(graphemes.reading_form())
# Output: ['フ', 'ジ']  <-- WRONG: should be ['フジ']

This occurs because the kanji 士 can be read as シ, so the algorithm interprets the ジ found in the grapheme's actual reading as an intentional change in voicing (i.e. rendaku) when in practice the grapheme 富士 cannot be split (although this may reveal a thing or two about historical changes in pronunciation, I wouldn't say it's particularly useful for parsing modern Japanese).

If this behavior is undesirable, simply disable the option to split graphemes affected by rendaku, at the cost of compound words such as 船橋 being treated as a single grapheme. May be fixed in a future update.

API Reference

Grapheme

A single grapheme.

Represents the smallest unit of written text that maintains its intended pronunciation. Can either be a single character or a multi-character compound with a distinct pronunciation.

Grapheme.reading_form()

The reading form of this grapheme (in katakana).

Grapheme.surface()

The original Japanese form of this grapheme.

GraphemeList

A list of graphemes.

GraphemeList.reading_form()

A list containing every grapheme's reading form (in katakana).

GraphemeList.surface()

A list containing every grapheme's original Japanese form.

split_graphemes()

Splits Japanese text into graphemes.

Args:

• japanese: The text to be split.
• split_rendaku: NOT RECOMMENDED: Use only if intending on verifying graphemes later on. This option may interpret compounds whose latter parts happen to be the voiced equivalents of unvoiced counterparts as examples of rendaku when they should not be considered as such. If True latter parts of a multi-kanji compound affected by rendaku (see https://en.wikipedia.org/wiki/Rendaku) are treated as separate graphemes.

Returns:

• A GraphemeList representing the split text.

Acknowledgements

This package relies on KANJIDIC dictionary files. These files are property of the Electronic Dictionary Research and Development Group (EDRDG) and are used in accordance with the Group's license.