# Ceteris Lab downloadable Python script
# Course: Fundamentals of Python for Financial Econometrics

import pandas as pd

df = pd.DataFrame({
    "province": ["ON", "ON", "QC", "QC"],
    "year": [2025, 2026, 2025, 2026],
    "income": [60, 63, 55, 58],
})
summary = df.groupby("province", as_index=False).agg(mean_income=("income", "mean"))
print(summary)

meta = pd.DataFrame({"province": ["ON", "QC"], "region": ["Central", "Central"]})
merged = df.merge(meta, on="province", how="left", validate="many_to_one", indicator=True)
print(merged.shape)
print(merged["_merge"].value_counts().to_dict())