finding percentage of a conditional group from the total at a column related to an event range from different column in pandas

Question

I have a Dataset like below :

How can I find the percentage of employees terminated at 2022 that First hire at 2021 from total employee using pandas?

employee No	Event date	Event Description
102	2021-10-12	First Hire
103	2021-11-02	First Hire
102	2022-01-01	Terminated
102	2021-12-12	Shift Change
101	2021-12-03	First Hire
103	2021-11-05	Terminated
101	2021-12-04	Terminated
105	2022-02-26	First Hire
106	2022-02-26	First Hire
102	2022-03-29	Second Hire
107	2021-05-04	First Hire
108	2022-04-04	First Hire
109	2022-03-03	Terminated
109	2021-12-29	First Hire
109	2022-04-01	Second Hire
109	2022-01-10	Shift Change

at the sample dataset Desired Condition belong to employee 109 and 102 how can find the condition at a dataset with 2M records .

Answer 1

# Convert Event Date to Timestamp if it's not Timestamp already
df["Event date"] = pd.to_datetime(df["Event date"])

# First hired in 2021
cond1 = df["Event date"].dt.year.eq(2021) & df["Event Description"].eq("First Hire")

# Terminated in 2022 & first hired in 2021
cond2 = (
    df["Event date"].dt.year.eq(2022)
    & df["Event Description"].eq("Terminated")
    & df["employee No"].isin(df.loc[cond1, "employee No"])
)

df[cond2]