On Wed, Dec 21, 2022 at 9:35 AM Chris Angelico <ros...@gmail.com> wrote:
> From the look of things, PyUnicode_Join (the internal function that > handles str.join()) uses a lot of "reaching into the data structure" > operations for efficiency. It uses PyUnicode_Check (aka "isinstance(x, > str)") rather than PyUnicode_CheckExact (aka "type(x) is str") and > then proceeds to cast the pointer and directly inspect its members. > > As such, I don't think UserString can ever truly be a str, I had figured subclasses of str wouldn’t be full players in the C code — but join() us pretty fundamental:-( -CHB -- Christopher Barker, PhD (Chris) Python Language Consulting - Teaching - Scientific Software Development - Desktop GUI and Web Development - wxPython, numpy, scipy, Cython
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