{1,2,7}.freeze() or {1,2,7}.to_frozenset() seem very natural and if this can be
optimized to avoid the copy, it's perfect.
For bytearray, one use case would be to optimise bytearray([1,2,7,2]) in
something like [1,2,7,2].to_byterray().
About bytes, one could have (1,2,7,2).to_bytes() instead of bytes((1,2,7,2))
because b'\x01\x02\x07\x02' is long and boring.
What about variables in the values {1,2,x}.freeze() should work too ?
bytes((1,2,7,x)) is not writable as a b string and creates a copy.
Le jeu. 12 juil. 2018 à 02:24, Chris Angelico
<ros...@gmail.com<mailto:ros...@gmail.com>> a écrit :
On Thu, Jul 12, 2018 at 10:13 AM, Gregory P. Smith
<g...@krypto.org<mailto:g...@krypto.org>> wrote:
>
> On Wed, Jul 11, 2018 at 4:45 PM Jelle Zijlstra
> <jelle.zijls...@gmail.com<mailto:jelle.zijls...@gmail.com>>
> wrote:
>> This could be done safely and without too much craziness if .freeze() on a
>> set returned a new frozenset. The compiler could then safely optimize {a,
>> set, literal}.freeze() into a frozenset literal, because methods on builtin
>> types cannot be monkeypatched. There's been talk of a similar optimization
>> on calls to .format() on string literals (not sure whether it's been
>> implemented).
>>
>> Whether implementing that is a good use of anyone's time is a different
>> question.
>
>
> Neat optimization. I hadn't considered that. We do know for sure it is a
> builtin type at that point.
>
> If that were implemented, bytes objects could gain a to_bytearray() (along
> the lines of the int.to_bytes() API) method that could be optimized away in
> literal circumstances.
Be careful: a bytearray is mutable, so this isn't open to very many
optimizations. A .freeze() method on sets would allow a set display to
become a frozenset "literal", stored as a constant on the
corresponding function object, the way a tuple is; but that's safe
because the frozenset doesn't need to concern itself with identity,
only value. Example:
def f(x):
a = (1, 2, 3) # can be optimized
b = (x, 4, 5) # cannot
c = [6, 7, 8] # cannot
Disassemble this or look at f.__code__.co_consts and you'll see (1, 2,
3) as a single constant; but the others have to be built.
+1 on set.freeze(); +0 on bytes.to_bytearray().
ChrisA
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