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https://issues.apache.org/jira/browse/ARROW-16580?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Fabien Aulaire updated ARROW-16580:
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Summary: [pyarrow][pandas conversion] Multiindex levels order is not
preserved after a from_pandas/to_pandas (was: [pyarrow][pandas conversion]
Multiindex levels are not preserved after a from_pandas/to_pandas)
> [pyarrow][pandas conversion] Multiindex levels order is not preserved after
> a from_pandas/to_pandas
> ----------------------------------------------------------------------------------------------------
>
> Key: ARROW-16580
> URL: https://issues.apache.org/jira/browse/ARROW-16580
> Project: Apache Arrow
> Issue Type: Bug
> Components: Python
> Affects Versions: 8.0.0
> Reporter: Fabien Aulaire
> Priority: Minor
>
> Hello,
> Not sure if it's the good place to report this issue but here is what I saw
> when I tried to convert a multi indexed dataframe (columns) to Table and
> convert it back to pandas:
>
> {code:python}
> import pandas as pd
> import pyarrow
> # pandas version '1.4.1'
> # pyarrow version '8.0.0'
> df = pd.DataFrame([[100,300, 400], [200,500, 600]], columns=['Toyota',
> 'Ford', 'Alfa'])
> concatenated = pd.concat([df, df*2], axis=1, keys=['foo', 'bar'])
> concatenated.columns.names = ['l1', 'l2']
> table = pyarrow.Table.from_pandas(concatenated)
> from_table_df = table.to_pandas()
> from_table_df.columns.levels # == FrozenList([['bar', 'foo'], ['Alfa',
> 'Ford', 'Toyota']])
> concatenated.columns.levels # == FrozenList([['foo', 'bar'], ['Toyota',
> 'Ford', 'Alfa']])
> {code}
> the order of columns levels is not preserved.
>
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