#0002

Group Records By Key

EasyPython12 min10 XP

Problem

Given a list of records and a key name, return a dictionary where each key value maps to the records with that value.

Why This Matters

Grouping rows is a core data skill. Before pandas groupby, you should understand the plain Python version.

Function Signature

def group_by(records, key):

Examples

Example 1

Inputrecords = [{"team": "A", "score": 10}, {"team": "B", "score": 8}, {"team": "A", "score": 7}], key = "team"

Output{"A": [{"team": "A", "score": 10}, {"team": "A", "score": 7}], "B": [{"team": "B", "score": 8}]}

Both team A records go under "A"; the team B record goes under "B".

Constraints

Every record contains the requested key.
Keep records in their original order inside each group.

CodePython

def group_by(records, key):
    """
    Input example: records = [{"team": "A", "score": 10}, {"team": "B", "score": 8}, {"team": "A", "score": 7}], key = "team"
    Return: {"A": [{"team": "A", "score": 10}, {"team": "A", "score": 7}], "B": [{"team": "B", "score": 8}]}
    Return the value from the function so the tests can compare it. Do not print unless the prompt asks.
    """
    groups = {}
    # write your code here
    return groups

def group_by(records, key):
    """
    Input example: records = [{"team": "A", "score": 10}, {"team": "B", "score": 8}, {"team": "A", "score": 7}], key = "team"
    Return: {"A": [{"team": "A", "score": 10}, {"team": "A", "score": 7}], "B": [{"team": "B", "score": 8}]}
    Return the value from the function so the tests can compare it. Do not print unless the prompt asks.
    """
    groups = {}
    # write your code here
    return groups

Visible browser tests run here when available.

Testcases1 visible / 3 hidden categories

Group by team

Input[{"team": "A", "score": 10}, {"team": "B", "score": 8}, {"team": "A", "score": 7}], "team"

Expected{"A": [...2 records...], "B": [...1 record...]}

The exact records are preserved; only the outer organization changes.

Hidden Test Categories

Single recordAll records in same groupMany groups with one record each