Joris Van den Bossche created ARROW-8442:
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             Summary: [Python] NullType.to_pandas_dtype inconsisent with dtype 
returned in to_pandas/to_numpy
                 Key: ARROW-8442
                 URL: https://issues.apache.org/jira/browse/ARROW-8442
             Project: Apache Arrow
          Issue Type: Bug
          Components: Python
            Reporter: Joris Van den Bossche


There is this behaviour of {{to_pandas_dtype}} returning float, while all 
actual conversions to numpy or pandas use object dtype:

{code}
In [23]: pa.null().to_pandas_dtype()                                            
                                                                                
                                                   
Out[23]: numpy.float64

In [24]: pa.array([], pa.null()).to_pandas()                                    
                                                                                
                                                   
Out[24]: Series([], dtype: object)

In [25]: pa.array([], pa.null()).to_numpy(zero_copy_only=False)                 
                                                                                
                                                   
Out[25]: array([], dtype=object)
{code}

So we should probably fix {{NullType.to_pandas_dtype}} to return object, which 
is used in practice.



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