encoder decorator

from functools import wraps


def encoder(m='ignore'):
    """
    The method m can be strict, replace and ignore.
    This decorator encodes arguments which are str.
    The output is decoded. Tuple, List, Dict and str is supported.
    """
    def fun(func):
        if m not in ['strict', 'ignore', 'replace']:
            raise Exception('use: stict, ignore, replace')
        @wraps(func)
        def inner(*args, **kwargs):
            func.__defaults__ = tuple([s.encode() if isinstance(s, str) else s for s in func.__defaults__])
            args = [a.encode(errors=m) if isinstance(a, str) else a for a in args]
            kwargs = {k: (v.encode(errors=m) if isinstance(v, str) else v) for k, v in kwargs.items()}
            ret = func(*args, **kwargs)
            if isinstance(ret, (tuple, list)):
                ret = [a.decode(errors=m) if isinstance(a, bytes) else a for a in ret]
            elif isinstance(ret, dict):
                ret = {k: (v.decode(errors=m) if isinstance(v, bytes) else v) for k, v in ret.items()}
            elif isinstance(ret, set):
                ret = {v.decode(errors=m) if isinstance(ret, bytes) else v for v in ret}
            elif isinstance(ret, bytes):
                ret = ret.decode(errors=m)
            return ret
        return inner
    return fun

@encoder()
def foo(a, b, c='20ööö'):
    print('a:', a)
    print('b:', b)
    print('c:', c)
    return [a, b, c]

if __name__ == '__main__':
    print(foo('ÄÄÄÄöööööüüüü???ßßßþþ', 'ABC'))