BUG: value_counts Int64 zero-size array to reduction

[mgsnuno]

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pandas.

• (optional) I have confirmed this bug exists on the master branch of pandas.

---

pd.Series([], dtype='int64').value_counts()  # Series([], dtype: int64)
pd.Series([], dtype='Int64').value_counts()  # ValueError: zero-size array to reduction ...

Problem description

Found this while using Int64 types in dask. Error occurred in _meta.value_counts()

Expected Output

Error not to occur.

Output of pd.show_versions()

INSTALLED VERSIONS

commit : None
python : 3.7.6.final.0
python-bits : 64
OS : Linux
OS-release : 4.19.113-1-MANJARO
machine : x86_64
processor :
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8

pandas : 1.0.3
numpy : 1.18.2
pytz : 2019.3
dateutil : 2.8.1
pip : 20.0.2
setuptools : 46.1.3.post20200325
Cython : None
pytest : 5.4.1
hypothesis : None
sphinx : None
blosc : 1.9.0
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : 2.11.1
IPython : 7.13.0
pandas_datareader: None
bs4 : 4.9.0
bottleneck : None
fastparquet : None
gcsfs : None
lxml.etree : None
matplotlib : 3.2.1
numexpr : None
odfpy : None
openpyxl : 3.0.3
pandas_gbq : None
pyarrow : 0.16.0
pytables : None
pytest : 5.4.1
pyxlsb : None
s3fs : 0.4.2
scipy : 1.4.1
sqlalchemy : 1.3.15
tables : None
tabulate : None
xarray : 0.15.1
xlrd : 1.2.0
xlwt : None
xlsxwriter : None
numba : 0.48.0

[simonjayhawkins]

Thanks @mgsnuno for the report. This issue didn't exist in 0.25.3 so marking as regression.

>>> import pandas as pd
>>>
>>> pd.__version__
'0.25.3'
>>>
>>> pd.Series([], dtype="int64").value_counts()
Series([], dtype: int64)
>>>
>>> pd.Series([], dtype="Int64").value_counts()
Series([], dtype: int64)
>>>

[simonjayhawkins]

This issue didn't exist in 0.25.3 so marking as regression.

raises from #30824 (i.e. 1.0.0)

8bdd7b1 is the first bad commit
commit 8bdd7b1
Author: Tom Augspurger [email protected]
Date: Thu Jan 9 13:19:34 2020 -0600

BUG: BooleanArray.value_counts dropna (#30824)

cc @TomAugspurger

[jreback]

@simonjayhawkins generally we don't mark experimental features as regressions, simply mark them as bugs.