[I] [Python] DataFrame Interchange Protocol - wrong dtype information for categorical columns [arrow]

["jorisvandenbossche (via GitHub)" <gi...@apache.org>]

jorisvandenbossche opened a new issue, #38034:
URL: https://github.com/apache/arrow/issues/38034

   Small example with a dictionary encoded column, and checking the dtype:
   
   ```
   In [59]: table = pa.table({'a': pa.array(["a", "b"]).dictionary_encode()})
   
   In [60]: table
   Out[60]: 
   pyarrow.Table
   a: dictionary<values=string, indices=int32, ordered=0>
   ----
   a: [  -- dictionary:
   ["a","b"]  -- indices:
   [0,1]]
   
   In [61]: obj = table.__dataframe__()
   
   In [62]: obj.get_column_by_name('a').dtype
   Out[62]: (<DtypeKind.CATEGORICAL: 23>, 32, 'L', '=')
   ```
   
   It correctly says that it is of kind "categorical", but then the bitwidth is 32 (because of int32 indices, so maybe correct?) and format string is "L" (uint64, so definitly wrong?)
   
   cc @AlenkaF 


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Re: [I] [Python] DataFrame Interchange Protocol - wrong dtype information for categorical columns [arrow]

["AlenkaF (via GitHub)" <gi...@apache.org>]

AlenkaF closed issue #38034: [Python] DataFrame Interchange Protocol - wrong dtype information for categorical columns
URL: https://github.com/apache/arrow/issues/38034


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