On 2022-01-16 08:27, Steven D'Aprano wrote: [snip]
dis.dis("frozenset({1, 2, 3})") 1 0 LOAD_NAME 0 (frozenset) 2 BUILD_SET 0 4 LOAD_CONST 0 (frozenset({1, 2, 3})) 6 SET_UPDATE 1 8 CALL_FUNCTION 1 10 RETURN_VALUE
Got that? To create a frozenset of literals, first the compiler creates a frozenset constant containing what you wanted. Then at runtime, it:
- looks up frozenset in globals and builtins; - loads the pre-prepared frozenset (which is exactly what we want); - creates a new set from that frozenset; - calls the frozenset() function on that set to create a new frozenset that duplicates the pre-prepared one; - and finally garbage-collects the temporary set.
[snip] Not quite as bad as that:
f = frozenset({1, 2, 3}) f is frozenset(f) True