replace placeholders enclosed in curly braces, like {thread}, {thread%10}, {thread/10}, with values

gistfile1.txt

class NumReplacer(dict):
    def __init__(self, **kwargs):
        dict.__init__(self, **kwargs)
    def __missing__(self, key):
        karr = key.split('%')
        if (len(karr) == 2) and karr[1].isdigit():
            value = dict.get(self, karr[0], None)
            if not value is None:
                mod = int(karr[1])
                return str(value % mod)
        karr = key.split('/')
        if (len(karr) == 2) and karr[1].isdigit():
            value = dict.get(self, karr[0], None)
            if not value is None:
                div = int(karr[1])
                return str(value // div)
        return "{" + key + "}"

def replace_num(s: str, **kwargs) -> str:
    return s.format_map(NumReplacer(**kwargs))

def main():
    print(replace_num("{thread},{regnum},{unknown}", thread=3, regnum=13))
    print(replace_num("{thread%10},{regnum%10},{unknown%10}", thread=5, regnum=23))
    print(replace_num("{thread/10},{regnum/10},{unknown/10}", thread=7, regnum=37))

if __name__ == '__main__':
    main()