[GitHub] [arrow] amol- commented on a change in pull request #10101: ARROW-9594: [Python] Preserve null indexes in DictionaryArray.to_numpy as it's done in DictionaryArray.to_pandas

[GitBox <gi...@apache.org>]

amol- commented on a change in pull request #10101:
URL: https://github.com/apache/arrow/pull/10101#discussion_r616000507



##########
File path: python/pyarrow/array.pxi
##########
@@ -1170,7 +1170,9 @@ cdef class Array(_PandasConvertible):
         array = PyObject_to_object(out)
 
         if isinstance(array, dict):
+            missings = array["indices"] < 0
             array = np.take(array['dictionary'], array['indices'])
+            array[missings] = np.NaN

Review comment:
       I thought about adding a `if missings.any():` here, but it didn't change performances at all, so not much benefit.
   
   ```
   def withoutcheck():
       arr[mask] = np.NaN
   
   def withcheck():
       if mask.any():
           arr[mask] = np.NaN
   
   >>> timeit.timeit(withoutcheck, number=10000)
   5.555068847000001
   >>> timeit.timeit(withcheck, number=10000)
   5.6257486310000075
   ```




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