正規表現バージョン

import re

TRANSUNIT = {'十': 10,
             '拾': 10,
             '百': 100,
             '千': 1000,
             '万': 10000,
             '億': 100000000,
             '兆': 1000000000000}

re_kunit = re.compile(
    "(?:(\d*)\s*(千)\s*)?(?:(\d*)\s*(百)\s*)?(?:(\d*)\s*([十拾])\s*)?(\d*)\s*([兆億万])|(?:(\d*)\s*(千)\s*)?(?:(\d*)\s*(百)\s*)?(?:(\d*)\s*([十拾])\s*)?(\d*)()")
knum = "一二三四五六七八九〇１２３４５６７８９０壱弐参"
anum = "12345678901234567890123"

def kanji2num(s):

    for i in range(len(anum)):
        s = s.replace(knum[i], anum[i])

    reg = re_kunit.findall(s)
    if not reg:
        return None

    ret = 0
    count = len(reg)
    for i in range(count):
        r = reg[i]

        digit = 0
        offset = 0
        if (not r[7]):
            offset = 4

        last_ar_idx = 2 * offset + 6
        last_ks_idx = last_ar_idx + 1

        for n in range(offset, offset + 3):
            ar = r[2 * n]
            ks = r[(2 * n) + 1]
            part = 1
            if ar:
                part *= int(ar)
            if ks:
                part *= TRANSUNIT[ks]
            if(part > 1):
                digit += part
        if(r[last_ar_idx]):
            digit += int(r[last_ar_idx])
        if(r[last_ks_idx]):
            digit *= TRANSUNIT[r[last_ks_idx]]

        ret += digit

    return ret


print(kanji2num("1億3千万百9十9")) # -> 130000199

正規表現使わないバージョン

上の正規表現は重いみたい

D1_UNIT = {
    '〇': 0, '一': 1, '二': 2, '三': 3, '四': 4, '五': 5,
    '六': 6, '七': 7, '八': 8, '九': 9, '０': 0, '１': 1,
    '２': 2, '３': 3, '４': 4, '５': 5, '６': 6, '７': 7,
    '８': 8, '９': 9, '0': 0, '1': 1, '2': 2, '3': 3,
    '4': 4, '5': 5, '6': 6, '7': 7, '8': 8, '9': 9,
    '零': 0, '壱': 1, '弐': 2, '参': 3,
}

D3_UNIT = {
    '千': 1000,
    '百': 100,
    '十': 10,
    '拾': 10,
}

LG_UNIT = {
    '京': 10000000000000000,
    '兆': 1000000000000,
    '億': 100000000,
    '万': 10000,
}

Collections = {
    ' ': '',     # delete
    '　': None,  # delete
    '，': ',',   # replace
    '、': ',',   # replace
    '．': '.',   # replace
    ',': ',',   # through(ignoring)
}

def kanji2int(val):
    if (not val):
        return None

    d1 = []
    large = 0
    total = 0
    result = ""

    numbuild = lambda n:n and int("".join(map(str, n))) or 0 ## // <- C++ very slow
    # numbuild = lambda n:n and sum(int(x) * 10 ** i for i, x in enumerate(reversed(n))) or 0 ## // for C++ memo

    for i, kn in enumerate(val):
        if (kn in Collections):
            if kn == Collections[kn] or not kn: # through or delete
                continue
            else:
                kn = Collections[kn]  # replace

        if (kn in D1_UNIT):
            d1.append(D1_UNIT[kn])
        elif (kn in D3_UNIT):
            large += (numbuild(d1) if d1 else 1) * D3_UNIT[kn]
            d1.clear()
        elif ((d1 or large) and kn in LG_UNIT):
            large += numbuild(d1)
            total += (large or 1) * LG_UNIT[kn]
            d1.clear()
            large = 0
        elif(kn == "." and d1[0] == 0):
            result += "0."
            d1.clear()
        else:
            if d1 and d1[0] == 0:
                result += "".join(map(str, d1))
            else:
                chk = total + large + numbuild(d1)
                if chk:
                    result += str(chk)
            result += kn
            d1.clear()
            large = 0
            total = 0

    return result or str(total + large + numbuild(d1))

print(kanji2int("1億3千万百9十9")) # -> 130000199