Sure: CPython doesn't know statically that anything is "not an object", so your proposal adds an extra test to every incref and every decref. This is perceived

Sure: CPython doesn't know statically that anything is "not an object", so your proposal adds an extra test to every incref and every decref. This is perceived as probably worse for performance. In 2002, a hacked CPython interpreter (source code long since lost, sorry!) saw a 5% performance decrease on pystone but a 14% performance increase on an integer-heavy workload. https://mail.python.org/pipermail/python-dev/2002-August/027685.html https://mail.python.org/pipermail/python-dev/2002-August/027...