#0119

Flag Duplicate Rows by Key

EasyPandas15 min10 XP

Problem

Given a DataFrame and list of key columns, return a copy with is_duplicate True for rows after the first occurrence of each key.

Why This Matters

Duplicate checks are a first-line data quality habit before analysis or training.

Function Signature

def flag_duplicates(df, keys):

Examples

Example 1

Inputids [1,1,2]

OutputFalse, True, False

Only the second row with id 1 is marked duplicate.

Constraints

Return the requested value exactly.
Handle the stated edge cases.
Keep the solution readable.

CodePython

import pandas as pd

def flag_duplicates(df, keys):
    """
    Input example: ids [1,1,2]
    Return: False, True, False
    Return the value from the function so the tests can compare it. Do not print unless the prompt asks.
    """
    # write your code here
    return df

import pandas as pd

def flag_duplicates(df, keys):
    """
    Input example: ids [1,1,2]
    Return: False, True, False
    Return the value from the function so the tests can compare it. Do not print unless the prompt asks.
    """
    # write your code here
    return df

Visible browser tests run here when available.

Testcases1 visible / 3 hidden categories

Core example

Inputids [1,1,2]

ExpectedFalse, True, False

Only the second row with id 1 is marked duplicate.

Hidden Test Categories

multiple key columnsno duplicatesall duplicates after first