loc on Series returning scalar when result size is 1

[omri374]

Code Sample

# Create a DataFrame with index and one Series
df = pd.DataFrame({"id":[1,2,3,3],"val":["abcde","bbcde","cbcde","dbcde"]})
df.set_index("id",inplace=True)

Calling .loc when the result length is 2 returns a Series (as expected):

type(df['val'].loc[3])

Output:

pandas.core.series.Series

Calling .loc when the result length is 1 returns a str:

# use .loc when the result length is 1:
type(df['val'].loc[1])

Output:

str

Problem description

The fact that the same code returns different types causes inconsistencies. If I run len on the result, I would get 2 for id=3 and 5 for id=1 or id=2, since the string length is 5:

len(df['val'].loc[3])

Output:

2

When calling loc[1]:

len(df['val'].loc[1])

Output:

5

Expected Output

.loc should return a Series regardless of the size. Otherwise this causes bugs when trying to evaluate the length of the output.

# Expected output:
type(df['val'].loc[1])

Output:

pandas.core.series.Series

len(df['val'].loc[1])

Output:

1

Output of pd.show_versions()

INSTALLED VERSIONS ------------------ commit : None python : 3.7.5.final.0 python-bits : 64 OS : Windows OS-release : 10 machine : AMD64 processor : Intel64 Family 6 Model 158 Stepping 10, GenuineIntel byteorder : little LC_ALL : None LANG : None LOCALE : None.None pandas : 0.25.3 numpy : 1.17.4 pytz : 2019.1 dateutil : 2.8.0 pip : 19.3.1 setuptools : 42.0.2.post20191203 Cython : None pytest : 5.3.2 hypothesis : None sphinx : None blosc : None feather : None xlsxwriter : None lxml.etree : None html5lib : None pymysql : None psycopg2 : None jinja2 : 2.10.3 IPython : 7.10.2 pandas_datareader: None bs4 : None bottleneck : None fastparquet : None gcsfs : None lxml.etree : None matplotlib : 3.1.1 numexpr : None odfpy : None openpyxl : None pandas_gbq : None pyarrow : None pytables : None s3fs : None scipy : 1.3.2 sqlalchemy : 1.3.12 tables : None xarray : None xlrd : 1.2.0 xlwt : None xlsxwriter : None

[jreback]

this is a duplicate issue - pls do a detailed search

[omri374]

Couldn't find the issue you refer to.

[jreback]

oldie but goodie
#9519

welcome to have go at impl
note this would be a breaking change so would need to simply deprecate things for now