DOC: DataFrame.count_values supports single label

[mattf]

Pandas version checks

• I have checked that the issue still exists on the latest versions of the docs on main here

Location of the documentation

https://pandas.pydata.org/docs/reference/api/pandas.DataFrame.value_counts.html

Documentation problem

documentation claims the subset must be list-like, optional

the implementation uses DataFrame.groupby, which accepts mapping, function, label, or list of labels

the result is value_counts can accept a single label

In [1]: import pandas as pd

In [2]: pd.__version__
Out[2]: '1.5.2'

In [3]: df = pd.DataFrame({"XYZ": ["foo", "foo", "foo", "foo", "foo"]})

In [4]: df.value_counts("XYZ")
Out[4]: 
XYZ
foo    5
dtype: int64

Suggested fix for documentation

1. change the value_counts documentation to reflect its capabilities
2. change the value_counts implementation to reflect the documentation

use of groupby goes to value_count's inception, and groupby's api has been consistent since 1.0

+1 option (1)

[mroeschke]

Thanks for the report. Additionally I don't see any testing of a single label subset so that would be good to add as well.

[tpackard1]

take