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https://issues.apache.org/jira/browse/ARROW-15765?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17497696#comment-17497696
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Joris Van den Bossche commented on ARROW-15765:
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In context of a full query plan, I think it is important to know the output
types given the input types, to be able to resolve the types in your full query?
I am wondering if we could make use of some of the newer typing features, which
would allow to do something like
{code:python}
def simple_function(arrow_array: pa.Array[pa.int32()]) -> pa.Array[pa.int32()]:
return call_function("add", [arrow_array, 1])
{code}
I think such an object with which you can use [] is called a "generic" in
typing terminology (https://docs.python.org/3.11/library/typing.html#generics),
and it would allow to more easily get the type of the values in the container.
On the other hand it creates a bit a separate typing syntax ({{pa.Array}} is
not actually itself a useful class, it's always subclasses you get in practice).
> [Python] Extracting Type information from Python Objects
> --------------------------------------------------------
>
> Key: ARROW-15765
> URL: https://issues.apache.org/jira/browse/ARROW-15765
> Project: Apache Arrow
> Issue Type: Improvement
> Components: C++, Python
> Reporter: Vibhatha Lakmal Abeykoon
> Assignee: Vibhatha Lakmal Abeykoon
> Priority: Major
>
> When creating user defined functions or similar exercises where we want to
> extract the Arrow data types from the type hints, the existing Python API
> have some limitations.
> An example case is as follows;
> {code:java}
> def function(array1: pa.Int64Array, arrya2: pa.Int64Array) -> pa.Int64Array:
> return pc.call_function("add", [array1, array2])
> {code}
> We want to extract the fact that array1 is an `pa.Array` of `pa.Int32Type`.
> At the moment there doesn't exist a straightforward manner to get this done.
> So the idea is to expose this feature to Python.
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