add furigana to kanji-hiragana pair

furigana.py

import re

f_nx = lambda x: x != ""

def rt_pattern(kanji, hira):
    return f"<ruby> {kanji} <rt> {hira} </rt></ruby>"

def to_furigana(kanji, hira):
    kana_range = "\u3040-\u30ff"
    re_kanj = f"([^{kana_range}]*)"
    re_kana = f"([{kana_range}]*)"
    is_hira = re.compile(f"[{kana_range}]+").search
    
    kj_l = re.split(f"([{kana_range}]+)", kanji) 
    kgr = list(filter(f_nx, kj_l))
    
    h_re = [f"({si})" if is_hira(si) else re_kana for si in kgr]
    hrex = "".join(h_re)
    
    hgr = re.search(hrex, hira).groups()
    
    assert len(hgr) == len(kgr)
    furi_l = [hgr[i] if hgr[i] == kgr[i] else rt_pattern(kgr[i], hgr[i]) for i in range(len(kgr))]
    
    return "".join(furi_l).strip()