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types: add PyMapping #1844

Merged
merged 1 commit into from
Sep 26, 2021
Merged

types: add PyMapping #1844

merged 1 commit into from
Sep 26, 2021

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davidhewitt
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Adds a PyMapping type - similar to PySequence, but specially to interact with the mapping protocol.

It doesn't have get_item, set_item, and del_item methods because they're already present because of Deref to PyAny. However it contains a few other helpful pieces such as .contains_key(), .keys(), .values(), and .items().

Seemed like it might be useful for davidhewitt/pythonize#16 (cc @i1i1)

WIP - needs tests.

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@birkenfeld birkenfeld left a comment

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As I proposed in #1845 for sequences, the API here should mirror PyDict as closely as possible.

K: ToBorrowedObject,
{
let r = key.with_borrowed_ptr(self.py(), |ptr| unsafe {
ffi::PyMapping_HasKey(self.as_ptr(), ptr)
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If we use HasKey which suppresses exceptions, the method can return just bool?

Otherwise, use GetItem internally to propagate the exceptions...

@davidhewitt
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👍 will update this to follow what you've done in #1849 but for PyDict / PyMapping

@davidhewitt
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Updated to contain the other relevant PyDict APIs and added tests.

In the end I couldn't come up with a good decision for .contains_key. I felt it was potentially confusing to implement it using PyMapping_HasKey, because the suppressed exception might not be a KeyError but some other cause (e.g. failed comparison when comparing two keys).

So for now I left .contains_key out.

@davidhewitt
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Any objections if I merge this?

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@birkenfeld birkenfeld left a comment

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Could add an entry in guide/src/conversions/tables.md I guess.

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👍 good idea, done!

@davidhewitt davidhewitt merged commit 16ac7d4 into PyO3:main Sep 26, 2021
@davidhewitt davidhewitt deleted the mapping-type branch September 26, 2021 13:56
@Gobot1234
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Is there a reason that contains_key wasn't implemented, it would be much better than obj.getattr("__contains__")?.call1((key,))?.is_true()?

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davidhewitt commented Dec 29, 2021

See #1844 (comment)

I just couldn't make an obvious decision on the semantics of contains_key in this initial PR. If you're willing to come up with an appropriate implementation and happy to open a PR for it, I'd be happy to add it to this type.

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Don't we have a method for the in operator on PyAny?

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Not that I could find?

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3 participants