Google ColabでPythonを動かしてみる

# =============================================================
# 複利計算シミュレータ（Google Colab対応）
# 月次複利・月次積立に対応。各セルにコピペして実行できます。
# =============================================================

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt

try:
    import japanize_matplotlib  # noqa: F401
except ImportError:
    print("※ 日本語表示が必要なら `!pip install japanize-matplotlib` を実行してください")


principal   = 1_000_000   # 初期元本（円）
monthly     = 50_000      # 毎月の積立額（円）
annual_rate = 0.05        # 年利（0.05 = 5%）
years       = 20          # 運用年数
freq        = 12          # 年あたりの複利・積立回数（12=月次, 1=年次）


def simulate(principal, monthly, annual_rate, years, freq=12):
    rate_per_period = annual_rate / freq
    n = years * freq
    balance = principal
    invested = principal
    rows = []
    for i in range(1, n + 1):
        balance *= (1 + rate_per_period)
        balance += monthly
        invested += monthly
        rows.append({
            "period": i, "year": i / freq,
            "balance": balance, "invested": invested,
            "gain": balance - invested,
        })
    return pd.DataFrame(rows)


df = simulate(principal, monthly, annual_rate, years, freq)

yearly = df[df["period"] % freq == 0].copy()
yearly["year"] = yearly["year"].astype(int)
summary = yearly[["year", "invested", "balance", "gain"]].reset_index(drop=True)
summary["gain_ratio"] = summary["gain"] / summary["invested"]

pd.options.display.float_format = lambda x: f"{x:,.0f}"
print("=== 年次サマリー ===")
print(summary.to_string(index=False))

final = df.iloc[-1]
print(f"\n運用年数: {years}年 / 累計投資額: {final['invested']:,.0f}円 / 最終資産: {final['balance']:,.0f}円 / 対投資額: {final['balance']/final['invested']:.2f}倍")

fig, ax = plt.subplots(figsize=(10, 6))
ax.plot(df["year"], df["balance"], label="資産（複利）", linewidth=2)
ax.plot(df["year"], df["invested"], label="累計投資額（元本）", linestyle="--", linewidth=2)
ax.fill_between(df["year"], df["invested"], df["balance"], alpha=0.2, label="評価益")
ax.set_xlabel("経過年数")
ax.set_ylabel("金額（円）")
ax.set_title(f"複利シミュレーション（年利{annual_rate*100:.1f}% / 月{monthly:,.0f}円積立）")
ax.legend()
ax.grid(True, alpha=0.3)
ax.yaxis.set_major_formatter(plt.FuncFormatter(lambda v, _: f"{v/1e6:.0f}M"))
plt.tight_layout()
plt.show()

# =============================================================
# 複利計算シミュレータ（Google Colab / インタラクティブ版）
# スライダー・入力欄でパラメータを変更すると即座に再計算されます。
# このコード全体を1つのセルに貼り付けて実行してください。
# =============================================================

import pandas as pd
import matplotlib.pyplot as plt
import ipywidgets as widgets
from IPython.display import display

try:
    import japanize_matplotlib  # noqa: F401
except ImportError:
    import subprocess, sys
    subprocess.run([sys.executable, "-m", "pip", "install", "-q",
                    "japanize-matplotlib"], check=True)
    import japanize_matplotlib  # noqa: F401


def simulate(principal, monthly, annual_rate, years, freq=12):
    rate_per_period = annual_rate / freq
    n = years * freq
    balance = principal
    invested = principal
    rows = []
    for i in range(1, n + 1):
        balance *= (1 + rate_per_period)
        balance += monthly
        invested += monthly
        rows.append({
            "period": i, "year": i / freq,
            "balance": balance, "invested": invested,
            "gain": balance - invested,
        })
    return pd.DataFrame(rows)


style = {"description_width": "120px"}
layout = widgets.Layout(width="420px")

w_principal = widgets.IntText(value=1_000_000, description="初期元本(円)", style=style, layout=layout)
w_monthly   = widgets.IntText(value=50_000, description="毎月積立(円)", style=style, layout=layout)
w_rate      = widgets.FloatSlider(value=5.0, min=0.0, max=15.0, step=0.1,
                                  description="年利(%)", readout_format=".1f",
                                  style=style, layout=layout)
w_years     = widgets.IntSlider(value=20, min=1, max=50, step=1,
                                description="運用年数", style=style, layout=layout)
w_freq      = widgets.Dropdown(options=[("月次", 12), ("年次", 1)], value=12,
                               description="複利・積立頻度", style=style, layout=layout)

out = widgets.Output()


def update(_=None):
    with out:
        out.clear_output(wait=True)
        df = simulate(w_principal.value, w_monthly.value,
                      w_rate.value / 100, w_years.value, w_freq.value)
        final = df.iloc[-1]

        print("=== 最終結果 ===")
        print(f"累計投資額   : {final['invested']:,.0f} 円")
        print(f"最終資産     : {final['balance']:,.0f} 円")
        print(f"評価益       : {final['gain']:,.0f} 円")
        print(f"対投資額倍率 : {final['balance'] / final['invested']:.2f} 倍")

        fig, ax = plt.subplots(figsize=(10, 5.5))
        ax.plot(df["year"], df["balance"], label="資産（複利）", linewidth=2)
        ax.plot(df["year"], df["invested"], label="累計投資額（元本）",
                linestyle="--", linewidth=2)
        ax.fill_between(df["year"], df["invested"], df["balance"], alpha=0.2, label="評価益")
        ax.set_xlabel("経過年数")
        ax.set_ylabel("金額（円）")
        ax.set_title(f"複利シミュレーション（年利{w_rate.value:.1f}% / 月{w_monthly.value:,.0f}円積立）")
        ax.legend()
        ax.grid(True, alpha=0.3)
        ax.yaxis.set_major_formatter(plt.FuncFormatter(lambda v, _: f"{v/1e6:.0f}M"))
        plt.tight_layout()
        plt.show()


for w in (w_principal, w_monthly, w_rate, w_years, w_freq):
    w.observe(update, names="value")

controls = widgets.VBox([w_principal, w_monthly, w_rate, w_years, w_freq])
display(controls, out)
update()