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Try not to throw around statements like “they broke duct ordering because they felt like it”. Obviously they didn’t do that. There are trade-offs when preservi

by orf 2y ago

Try not to throw around statements like “they broke duct ordering because they felt like it”. Obviously they didn’t do that. There are trade-offs when preserving dictionary ordering.

actionfromafar 2y ago
The trade-off is a bit of speed.
- cjbillington 2y ago
  This might be what you meant, but the ordered dicts are faster, no? I believe ordering was initially an implementation detail that arose as part of performance optimisations, and only later declared officially part of the spec.
  - Someone 2y ago
    > but the ordered dicts are faster, no? They may be in the current implementations, but removing an implementation constraint can only increase the solution space, so it cannot make the best implementation slower. As a trivial example, the current implementation that guarantees iteration happens in insertion order also is a valid implementation for a spec that does not require that guarantee.
dathinab 2y ago
if you claim > high-performance Python implementation then no this aren't trade-offs but breaking the standard without it truly being necessary most important this will break code in a subtle and potentially very surprising way they could just claim they are python like and then no one would hold them for not keeping to the standard but if you are misleading about your product people will find offense even if it isn't intentionally
baq 2y ago
dicts ordering keys in insertion order isn't an implementation detail anymore and hasn't been for years.
- nick238 2y ago
  I get that all dicts are now effectively an `collections.OrderedDict`, but I've never seen practical code that uses the insertion order. You can't do much with that info (no `.pop()`, can't sort a dict without recreating it) beyond maybe helping readability when you print or serialize it.
  - funny_falcon 2y ago
    Readability, reproducibility, and simple LRU. Reproducibility matters for tests, they become simpler. Some other algorithms become simpler as well. LRU is just a dict with preserving order: on access just delete and insert again.

by orf 2y ago

Try not to throw around statements like “they broke duct ordering because they felt like it”. Obviously they didn’t do that. There are trade-offs when preserving dictionary ordering.

actionfromafar 2y ago

The trade-off is a bit of speed.

cjbillington 2y ago
This might be what you meant, but the ordered dicts are faster, no? I believe ordering was initially an implementation detail that arose as part of performance optimisations, and only later declared officially part of the spec.
- Someone 2y ago
  > but the ordered dicts are faster, no? They may be in the current implementations, but removing an implementation constraint can only increase the solution space, so it cannot make the best implementation slower. As a trivial example, the current implementation that guarantees iteration happens in insertion order also is a valid implementation for a spec that does not require that guarantee.

dathinab 2y ago

if you claim > high-performance Python implementation then no this aren't trade-offs but breaking the standard without it truly being necessary most important this will break code in a subtle and potentially very surprising way they could just claim they are python like and then no one would hold them for not keeping to the standard but if you are misleading about your product people will find offense even if it isn't intentionally

baq 2y ago

dicts ordering keys in insertion order isn't an implementation detail anymore and hasn't been for years.

nick238 2y ago
I get that all dicts are now effectively an `collections.OrderedDict`, but I've never seen practical code that uses the insertion order. You can't do much with that info (no `.pop()`, can't sort a dict without recreating it) beyond maybe helping readability when you print or serialize it.
- funny_falcon 2y ago
  Readability, reproducibility, and simple LRU. Reproducibility matters for tests, they become simpler. Some other algorithms become simpler as well. LRU is just a dict with preserving order: on access just delete and insert again.