[
https://issues.apache.org/jira/browse/ARROW-6486?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Wes McKinney closed ARROW-6486.
-------------------------------
Resolution: Won't Fix
> [Python] Allow subclassing & monkey-patching of Table
> -----------------------------------------------------
>
> Key: ARROW-6486
> URL: https://issues.apache.org/jira/browse/ARROW-6486
> Project: Apache Arrow
> Issue Type: Improvement
> Components: Python
> Reporter: ARF
> Priority: Major
> Labels: pull-request-available
> Time Spent: 1h 50m
> Remaining Estimate: 0h
>
> Currently, many classes in {{pyarrow}} behave strangely to the Python user:
> they are neither subclassable not monkey-patchable.
>
> {{>>> import pyarrow as pa}}
> {{>>> class MyTable(pa.Table):}}
> {{... pass}}
> {{...}}
> {{>>> table = MyTable.from_arrays([], [])}}
> {{>>> type(table)}}
> {{<class 'pyarrow.lib.Table'>}}
> The factory method did not return an instance of our subclass...
> Never mind, let's monkey-patch {{Table}}:
> {{>>> pa.TableOriginal = pa.Table}}
> {{>>> pa.Table = MyTable}}
> {{>>> table = pa.Table.from_arrays([], [])}}
> {{>>> type(table)}}
> {{<class 'pyarrow.lib.Table'>}}
>
> OK, that did not work either.
> Let's be sneaky:
> {{>>> table.__class__ = MyTable}}
> {{Traceback (most recent call last):}}
> \{{ File "<stdin>", line 1, in <module>}}
> {{TypeError: __class__ assignment only supported for heap types or
> ModuleType subclasses}}
> {{>>>}}
>
> There is currently no way to modify or extend the behaviour of a {{Table}}
> instance. Users can use only what {{pyarrow}} provides out of the box. - This
> is likely to be a source of frustration for many python users.
>
> The attached PR remedies this for the {{Table}} class:
> {{>>> import pyarrow as pa}}
> {{>>> class MyTable(pa.Table):}}
> {{... pass}}
> {{...}}
> {{>>> table = MyTable.from_arrays([], [])}}
> {{>>> type(table)}}
> {{<class '__main__.MyTable'>}}
> {{>>>}}
> {{>>> pa.TableOriginal = pa.Table}}
> {{>>> pa.Table = MyTable}}
> {{>>> table = pa.Table.from_arrays([], [])}}
> {{>>> type(table)}}
> {{<class '__main__.MyTable'>}}
> {{>>>}}
>
> Ideally, these modifications would be extended to the other cython-defined
> classes of {{pyarrow}}, but given that Table is likely to be the interface
> that most users begin their interaction with, I thought this would be a good
> start.
> Keeping the changes limited to a single class should also keep merge
> conflicts manageable.
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