股息再投资计算器

def drip_calculator(
    initial: float,
    annual_yield: float,
    annual_growth: float,
    years: int,
    periods_per_year: int = 4  # quarterly
) -> list[dict]:
    """Calculate DRIP portfolio growth year by year."""
    period_yield = annual_yield / 100 / periods_per_year
    period_growth = (1 + annual_growth / 100) ** (1 / periods_per_year)

    portfolio = initial
    results = []

    for year in range(1, years + 1):
        year_dividends = 0
        for _ in range(periods_per_year):
            div = portfolio * period_yield
            year_dividends += div
            portfolio = (portfolio + div) * period_growth

        results.append({
            "year": year,
            "portfolio_value": round(portfolio, 2),
            "year_dividends": round(year_dividends, 2),
        })

    return results

results = drip_calculator(
    initial=10000,
    annual_yield=4.0,
    annual_growth=7.0,
    years=20,
    periods_per_year=4
)
for r in results[-5:]:
    print(f"Year {r['year']}: ${r['portfolio_value']:,.2f} (dividends: ${r['year_dividends']:,.2f})")