thisisnic commented on PR #45818:
URL: https://github.com/apache/arrow/pull/45818#issuecomment-2823427616
@pitrou - I've implemented most of the changes suggested in your original
issue, but the one I'm stuck on is the example you gave:
```
>>> a, b = pc.min_max([1,2,3])
>>> a # expecting 1
'min'
>>> b # expecting 3
'max'
```
This happens because the compute function returns a StructScalar and in the
`__iter__()` method for StructScalars, we return keys and not values. This
seems analagous to how Python dictionaries work, e.g.
```
>>> a, b = {'min': 1, 'max': 3}
>>> a
'min'
>>> b
'max'
```
I tried updating it to return values instead of keys, but this introduces a
load of breaking changes in the tests as we're now fundamentally changing how
StructScalars work.
```
1. FAILED
pyarrow/tests/test_scalars.py::test_basics[builtin_pickle-value35-None-StructScalar]
- TypeError: Expected integer or string index
2. FAILED pyarrow/tests/test_scalars.py::test_map[builtin_pickle] -
ValueError: Converting to Python dictionary is not supported when duplicate
field names are present
3. FAILED pyarrow/tests/test_scalars.py::test_struct - AssertionError:
assert [2, 3.5] == ['x', 'y']
4. FAILED pyarrow/tests/test_scalars.py::test_struct_duplicate_fields -
AssertionError: assert [1, 2.0, 3] == ['x', 'y', 'x']
5. FAILED
pyarrow/tests/test_scalars.py::test_nested_map_types_with_maps_as_pydicts -
TypeError: Expected integer or string index
```
It feels like this could have significant user impact. Is it desirable to
make such an in-depth change to how StructScalars work, or do you reckon we
should just document that users should do something like use `items()` to get
these values, like this?
```
>>> a, b = pc.min_max([1,2,3]).items()
>>> a
('min', <pyarrow.Int64Scalar: 1>)
>>> b
('max', <pyarrow.Int64Scalar: 3>)
```
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