#0130

Count Records by Two Fields

MediumPython25 min20 XP

Problem

Given records and two field names, return a dictionary mapping (field1_value, field2_value) tuples to counts.

Why This Matters

Multi-key grouping is used in dashboards, cohort tables, and feature crosses.

Function Signature

def count_by_pair(records, first, second):

Examples

Example 1

Input[{"city":"NY","plan":"pro"}, {"city":"NY","plan":"pro"}, {"city":"LA","plan":"free"}]

Output{("NY","pro"): 2, ("LA","free"): 1}

The tuple combines both grouping fields.

Constraints

Return the exact requested structure.
Handle normal edge cases cleanly.
Prefer readable code over clever shortcuts.

CodePython

def count_by_pair(records, first, second):
    """
    Input example: [{"city":"NY","plan":"pro"}, {"city":"NY","plan":"pro"}, {"city":"LA","plan":"free"}]
    Return: {("NY","pro"): 2, ("LA","free"): 1}
    Return the value from the function so the tests can compare it. Do not print unless the prompt asks.
    """
    # write your code here
    return {}

def count_by_pair(records, first, second):
    """
    Input example: [{"city":"NY","plan":"pro"}, {"city":"NY","plan":"pro"}, {"city":"LA","plan":"free"}]
    Return: {("NY","pro"): 2, ("LA","free"): 1}
    Return the value from the function so the tests can compare it. Do not print unless the prompt asks.
    """
    # write your code here
    return {}

Visible browser tests run here when available.

Testcases1 visible / 3 hidden categories

Core example

Input[{"city":"NY","plan":"pro"}, {"city":"NY","plan":"pro"}, {"city":"LA","plan":"free"}]

Expected{("NY","pro"): 2, ("LA","free"): 1}

The tuple combines both grouping fields.

Hidden Test Categories

empty recordsall unique pairssame first field different second field