通过使用 pandas 在循环中比较列和变量来为列分配值

Question

I have two columns, one with students names and other is just empty. I have a list containing the students names who have passed. so in for loop, I will be taking each name from list and compare it with first column values. If name found in the column, then add "Pass" in the econd column corresponding to that name.

Have to go through each value in list and fill the PASS/FAIL in the second column. But the issue is, I dont know how to pass variable name in pandas condition. if I pass the value of variable directly, it works. Could someone suggest, how to pass variable name instead of value directly.

    df.loc[df['student_name'] == "John", 'status'] = "Pass"
    

I want to replace this name "John" with variable name (passed_students) from loop which will be like:

      df.loc[df['student_name'] == passed_students, 'status'] = "Pass"

But it is throwing "KeyError: 'student_name'"

Answer 1

Use the .isin() function to vectorize the operation.

import pandas as pd
import string
import numpy as np

## create dummy data
df = pd.DataFrame({"students":list(string.ascii_lowercase[:26]),"status":"Failed"})
passed_students = list(string.ascii_lowercase[:6])

print(df.head())
##look for students who have passed and assign "Passed" status.
df.loc[df.students.isin(passed_students),"status"] = "Passed"
print(df.head())