Calculate age from given date string with prefix and postfix (RU)

age_str_calc.py

def age_str_calc(date: str, strp_format: str, bounds=(1, 120)) -> tuple:
    '''Calulate age from given date, if age fit the bounds (default is 1-120 years),
    then return string: prefix (RU) + age (in years) + postfix (RU). Otherwise return empty string.'''
    def age(birthdate: object) -> int:
        '''Return age (int) by given datetime object'''
        today = datetime.date.today()
        age = today.year - birthdate.year - (
            (today.month, today.day) < (birthdate.month, birthdate.day)
            )
        return age

    age = age(dt.strptime(date, strp_format).date())

    if age < bounds[0] or age > bounds[1]:
        return ''
    else:
        prefix = 'Возраст:'
        if 5 <= age <= 20:
            postfix = 'лет'
        elif int(repr(age)[-1]) % 10 == 1:
            postfix = 'год'
        elif 2 <= int(repr(age)[-1]) % 10 <= 4:
            postfix = 'года'
        else:
            postfix = 'лет'
        return ' '.join((prefix, str(age), postfix))