DOC: Undocumented change in .isin behavior from 1.1.5 to 1.2.0 #38781
Description
Location of the documentation
https://pandas.pydata.org/docs/whatsnew/v1.2.0.html
Documentation problem
There seems to be an undocumented change with how isin works.
pandas 1.1.5:
import pandas as pd
pd.Series([0]).isin(['0'])
# 0 True
# dtype: bool
pd.Series([1]).isin(['1'])
# 0 True
# dtype: bool
pd.Series([1.1]).isin(['1.1'])
# 0 True
# dtype: boolBut in pandas 1.2.0 (and 1.2.0rc):
import pandas as pd
pd.Series([0]).isin(['0'])
# 0 False
# dtype: bool
pd.Series([1]).isin(['1'])
# 0 False
# dtype: bool
pd.Series([1.1]).isin(['1.1'])
# 0 False
# dtype: boolBut the release notes mentions nothing about it.
I have not posted this issue as an bug, because I think the newer implementation is the better implementation.
However I propose adding the change to the release notes for other people like me where the change broke tests in a pipeline.
Suggested fix for documentation
Add a line mentioning that isin no longer returns true when comparing floats to a string of the float.