[Python-3000] bytes and dicts (was: PEP 3137: Immutable Bytesand Mutable Buffer)

[Terry Reedy]

"Guido van Rossum" <guido at python.org> wrote in message 
news:ca471dc20709281140q2ef95c2ap8bbc7b7d3d46ebc0 at mail.gmail.com...
|
| Well, if we wanted "x" and b"x" to compare unequal instead of raising
| an exception, we could just define it that way (it was that way until
| just before 3.0a1). But we're explicitly defining it to raise a
| TypeError so as to catch buggy code. I think trying to fix dict lookup
| so that it, and only it, treats this as unequal, would be adding too
| many quirks.
|
| We could choose to kill the TypeError altogether. If we keep it, we
| should consistently let it raise TypeError everywhere.
|
| 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. 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.
|
| So, I think that after all this was a bad idea. Sorry.

If you mean making a special case exception for string/bytes equality test, 
I agree.  Would a restricted key dict (say, rdict, in collections) solve 
the problem you are aiming at?

import collections
adict = rdict(str)
bdict = rdict(bytes)

Now any buggy insertions get caught.

Terry J. Reedy