BUG: Series.round() expects ExtensionArray.round() to be implemented

[andrewgsavage]

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Reproducible Example

import pandas as pd
import pint
import pint_pandas

s = pd.Series([1.2345678, 2.3456789])
s.round(2)

df_pint = pd.DataFrame([1.2345678, 2.3456789], dtype='pint[m]')
df_pint.round(2)


s_pint = pd.Series([1.2345678, 2.3456789], dtype='pint[m]')
s_pint.round(2) # this errors

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
Input In [19], in <cell line: 13>()
      9 df_pint.round(2)
     12 s_pint = pd.Series([1.2345678, 2.3456789], dtype='pint[m]')
---> 13 s_pint.round(2)

File ~\anaconda3\envs\pint-pandas-oct22\lib\site-packages\pandas\core\series.py:2602, in Series.round(self, decimals, *args, **kwargs)
   2570 """
   2571 Round each value in a Series to the given number of decimals.
   2572 
   (...)
   2599 dtype: float64
   2600 """
   2601 nv.validate_round(args, kwargs)
-> 2602 result = self._values.round(decimals)
   2603 result = self._constructor(result, index=self.index).__finalize__(
   2604     self, method="round"
   2605 )
   2607 return result

AttributeError: 'PintArray' object has no attribute 'round'

Issue Description

Series.round() expects ExtensionArray.round() to be implemented. ExtensionArray.round() isn't mentioned in any docs, so I'm suprised to see this error. Should EAs implement a round method?

Some previous discussion here, but with a different error message #26730

Expected Behavior

A note in EA docs to implement round if that's needed.

Installed Versions

INSTALLED VERSIONS

commit : 91111fd
python : 3.10.6.final.0
python-bits : 64
OS : Windows
OS-release : 10
Version : 10.0.19044
machine : AMD64
processor : Intel64 Family 6 Model 151 Stepping 2, GenuineIntel
byteorder : little
LC_ALL : None
LANG : None
LOCALE : English_United Kingdom.1252

pandas : 1.5.1
numpy : 1.23.3
pytz : 2022.1
dateutil : 2.8.2
setuptools : 63.4.1
pip : 22.2.2
Cython : None
pytest : 7.2.0
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : None
IPython : 8.4.0
pandas_datareader: None
bs4 : None
bottleneck : 1.3.5
brotli : None
fastparquet : None
fsspec : None
gcsfs : None
matplotlib : 3.5.2
numba : None
numexpr : 2.8.3
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : None
pyreadstat : None
pyxlsb : None
s3fs : None
scipy : None
snappy : None
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
xlwt : None
zstandard : None
tzdata : None

[codestorm177]

Thank you for giving a detailed description. Looking into this now

[topper-123]

ExtensionArray can hold data that don't require a round method, I don't think this is an issue with ExtensionArray itself.

Probably there should be an abstract round method in ExtensionOpsMixin.