[jira] [Commented] (ARROW-9096) [Python] Pandas roundtrip with object-dtype column labels with integer values: data type "integer" not understood

["Andrew Wieteska (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-9096?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17164014#comment-17164014 ] 

Andrew Wieteska commented on ARROW-9096:
----------------------------------------

ARROW-3651 is related, I think

> [Python] Pandas roundtrip with object-dtype column labels with integer values: data type "integer" not understood
> -----------------------------------------------------------------------------------------------------------------
>
>                 Key: ARROW-9096
>                 URL: https://issues.apache.org/jira/browse/ARROW-9096
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: Python
>    Affects Versions: 0.17.1
>            Reporter: Richard Wu
>            Priority: Minor
>
> The following will fail the roundtrip since the column indexes' pandas_type is converted from int64 to integer when an additional column is introduced and subsequently moved to the index:
>  
> {code:java}
> df = pd.DataFrame(np.ones((3,1), index=[[1,2,3]])
> df['foo'] = np.arange(3)
> df = df.set_index('foo', append=True)
> table = pyarrow.Table.from_pandas(df)
> table.to_pandas()  # Errors{code}



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