[Python-3000] bytes & Py_TPFLAGS_BASETYPE (original) (raw)

Guido van Rossum guido at python.org
Sun Sep 16 19:02:09 CEST 2007

It is possible to compromise the integrity of a built-in type by subclassing it if the type wasn't carefully written to expect subclassing. The bytes type currently wasn't written to be careful about this. Why can't you use containment instead of subclassing?

--Guido

On 9/16/07, Mathieu Fenniak <mathieu.fenniak at gmail.com> wrote:

Hi everyone,

I'd like to be able to derive from the bytes type, but this currently isn't possible due to it missing the PyTPFLAGSBASETYPE. A comment next to the flags indicates that this class is "sealed / final". I tried to search this list for some information on this, but I couldn't find any relevant posts. Why is this type "sealed"? I've experimented by adding the basetype flag to the type (with a recent svn checkout). Python's test suite continues to run without any errors after this change. My own project's test suite works flawlessly with a bytes derived type, as well. I expected to encounter some error or difficulty that would explain why this type wasn't usable as a base type, but it seems to work great. Mathieu

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-- --Guido van Rossum (home page: http://www.python.org/~guido/)

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