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From: Ian Kelly <ian.g.kelly@gmail.com>
Date: Sun, 12 Oct 2014 12:45:14 -0600
Subject: Re: TypeError: 'kwarg' is an invalid keyword argument for this function
To: Python <python-list@python.org>
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On Sun, Oct 12, 2014 at 6:55 AM, roro codeath <rorocodeath@gmail.com> wrote:
> How to implement it in my class?
>
> class Str(str):
>     def __init__(self, *args, **kwargs):
>         pass
>
> Str('smth', kwarg='a')

The error is coming from the __new__ method. Because str is an
immutable type, you should override the __new__ method, not __init__.
Example:

class Str(str):
    def __new__(cls, *args, **kwargs):
        return super().__new__(cls, args[0])

>>> Str('smth', kwarg='a')
'smth'