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https://issues.apache.org/jira/browse/ARROW-13784?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17406588#comment-17406588
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Joris Van den Bossche commented on ARROW-13784:
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Actually, we already check that the list of arrays and list of names should
have the same length. But, in the special case of a list of arrays of length
zero, we return just before that:
https://github.com/apache/arrow/blob/26a34c3a2300620787806c5a8cee08ff30610e3e/python/pyarrow/table.pxi#L557-L569
So by moving the {{if len(names) != K:}} check before the {{if K == 0}} check,
this should be fixed.
> [Python] Table.from_arrays should return a schema when array is empty but
> names is not
> --------------------------------------------------------------------------------------
>
> Key: ARROW-13784
> URL: https://issues.apache.org/jira/browse/ARROW-13784
> Project: Apache Arrow
> Issue Type: Bug
> Components: Python
> Affects Versions: 4.0.1
> Reporter: Abderrahmane Jaidi
> Priority: Major
> Labels: good-first-issue
>
> The `Table.from_arrays` method returns an empty schema when supplying an
> empty arrays list but providing column names. As a result, the subsequent
> `to_pandas` method returns an empty data frame with no column names.
> ```
> {{import pyarrow as pa}}
> {{arrays = []}}
> {{cols_names = ["col1", "col2"]}}
> {{table = pa.Table.from_arrays(arrays=arrays, names=cols_names)}}
> {{table.schema # returns nothing}}
> {{df = table.to_pandas()}}
> {{df.head()}}
> {{Empty DataFrame
> Columns: []
> Index: [] # Expected column names to be visible here}}
> ```
> I assume that this is because a schema cannot be built without data types?
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