[Python-3000] bytes and dicts (was: PEP 3137: Immutable Bytes and Mutable Buffer) (original) (raw)
Jim Jewett jimjjewett at gmail.com
Fri Sep 28 21:02:59 CEST 2007
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On 9/28/07, Guido van Rossum <guido at python.org> wrote:
The question is whether it's worth the effort to raise TypeError when the potential exists that a certain hash sequence could raise this TypeError.
Bugs depending on the hash sequence are exactly the sort of thing that doesn't get found by tests, and can't be easily reproduced.
I'm less and less convinced -- after all, we're making the exception only for bytes/str, not for other types that might raise TypeError upon comparison.
What would those other types be?
As you point out in the "Bytes and the Str Type" section, this exception violates the "general rule that comparing objects of different types for equality should just return False".
In Py3, there are plenty of types that aren't orderable, but I still can't think of any[*] others that raise an exception when tested just for equality.
[*] It is of course possible to write a malicious class, and it is possible to write a buggy class. Even then, most buggy classes fail when compared to anything from any other class, rather than just for specific banned comparisons.
-jJ
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