Solar Installer Monthly Activity (2021)

PandasHardSenior level~10 min

Problem

A solar-panel company keeps three DataFrames. `installers` (`installer_id`, `onboarded_on`) records when each installer joined. `requests` (`request_id`, `household_id`, `requested_on`) records install requests from households. `bookings` (`request_id`, `installer_id`, `panel_count`, `job_minutes`) records each request that was actually booked to an installer.\n\nFor **each of the 12 months of 2021**, report two numbers:\n- `active_installers` — installers considered active that month: anyone onboarded before 2021, plus anyone onboarded in 2021 in that month or earlier (an installer is active from their onboarding month onward, and forever after).\n- `booked_requests` — the number of bookings whose underlying request was made in 2021 in that month.\n\nReturn columns `month` (1-12), `active_installers`, `booked_requests`. Rows may be in any order.

Input data

Example rows — the live problem includes the full dataset.

installers

installer_id	onboarded_on
10	2020-12-10
8	2021-01-13
5	2021-02-16
7	2021-03-08
4	2021-05-17

requests

request_id	household_id	requested_on
6	75	2020-12-09
1	54	2021-02-09
10	63	2021-03-04
19	39	2021-04-06
3	41	2021-06-03

bookings

request_id	installer_id	panel_count	job_minutes
10	10	63	38
13	10	73	96
7	8	100	28
17	7	119	68
20	1	121	92

Expected output

Your answer should return 12 rows with the columns month, active_installers, booked_requests.

Starter code (Pandas (Python))

import pandas as pd

def solar_monthly_activity(installers, requests, bookings) -> pd.DataFrame:
    # Your code here
    return installers

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