[Tim]

Question: Should we complain if someone tries to intern an instance of a string subclass? I hate to slow any code on those paths.

[Guido]

I think in this case intern(s) should return intern(str(s)). The fast path checks ob_sinterned first, and that should always point to a real string for a string subclass.

I think I'm wrestling with more than one problem here. The bogus one confusing everything else appears to be this:

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class S(str): ... pass ... [7098 refs] hash(S('abc')) 0 [7100 refs] hash(S('cdefg')) 0 [7102 refs]

That is, PyObject_Hash(s) is always 0 for any instance s of a subclass of str. This makes dict-based operations "almost always" believe that an s like this used as a key doesn't match a real string with the same value.

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d = {'a': 1} [7106 refs] d[S('a')] Traceback (most recent call last): File "<stdin>", line 1, in ? KeyError: a [7143 refs]

This applies too to the intern dict. So first I think str_subtype_new has to finish initializing the subclass string object. Then I can get confused about interning for the right reasons <wink>.