[Python] accept pyarrow values / scalars in constructor functions ? #21761
Description
Currently, functions like `pyarrow.array` don't accept pyarrow Arrays, or also not scalars of it:
In [42]: arr = pa.array([1, 2, 3])
In [43]: pa.array(arr)
...
ArrowInvalid: Could not convert 1 with type pyarrow.lib.Int64Value: did not recognize Python value type when inferring an Arrow data type
In [44]: pa.array(list(arr))
...
ArrowInvalid: Could not convert 1 with type pyarrow.lib.Int64Value: did not recognize Python value type when inferring an Arrow data typeDo we want to allow those / recognize those here? (the first case could even have a fastpath, as we don't need to do it element by element).
Also scalars are not supported:
In [46]: type(arr.sum())
Out[46]: pyarrow.lib.Int64Scalar
In [47]: pa.array([arr.sum()])
...
ArrowInvalid: Could not convert 6 with type pyarrow.lib.Int64Scalar: did not recognize Python value type when inferring an Arrow data typeAnd also in other functions we don't accept arrow scalars / values:
In [48]: string = pa.array(['a'])[0]
In [49]: type(string)
Out[49]: pyarrow.lib.StringValue
In [50]: pa.field(string, pa.int64())
...
TypeError: expected bytes, pyarrow.lib.StringValue found
Reporter: Joris Van den Bossche / @jorisvandenbossche
Related issues:
- [Python] pa.array() doesn't support pa.lib.TimestampScalar objects (duplicates)
- [Python] Array constructor doesn't support arrow scalars. (is duplicated by)
- [Python] Scalar constructors should be callable (relates to)
- [Python] Allow pa.array/pa.chunked_array to infer pa.NA when in a non pyarrow container (relates to)
Note: This issue was originally created as ARROW-5295. Please see the migration documentation for further details.