app.py

## pip install Flask

import io
import base64

import matplotlib.pyplot as plt
from flask import Flask, render_template, request


app = Flask(__name__)

@app.route('/', methods=['GET', 'POST'])
def index():
    if request.method == 'POST':
        initial_deposit = float(request.form['initial_deposit'])
        interest_rate = float(request.form['interest_rate'])
        contribution = float(request.form['contribution'])
        compounding_type = request.form['compounding_type']
        time_period_years = int(request.form['time_period_years'])

        if compounding_type == 'annual':
            n = 1
        elif compounding_type == 'monthly':
            n = 12

        ## Calculate final amount with interest
        total_amount = initial_deposit * (1 + interest_rate / n) ** (n * time_period_years)
        total_contributions = contribution * (((1 + interest_rate / n) ** (n * time_period_years) - 1) / (interest_rate / n))
        final_amount_with_interest = total_amount + total_contributions

        ## Calculate final amount without interest (just contributions)
        final_amount_without_interest = initial_deposit + contribution * time_period_years * n
        difference = final_amount_with_interest - final_amount_without_interest

        amounts_with_interest = []
        amounts_without_interest = []

        years = list(range(time_period_years + 1))

        for year in years:
            year_total_amount = initial_deposit * (1 + interest_rate / n) ** (n * year)
            year_total_contributions = contribution * (((1 + interest_rate / n) ** (n * year) - 1) / (interest_rate / n))

            year_total_contributions_without_interest = initial_deposit + contribution * year * n
            
            amounts_with_interest.append(year_total_amount + year_total_contributions)
            amounts_without_interest.append(year_total_contributions_without_interest)

        
        plt.figure(figsize=(10, 5))
        plt.plot(years, amounts_with_interest, marker='o', label='With Interest')
        plt.plot(years, amounts_without_interest, marker='o', label='Without Interest')
        plt.title("Compound Interest Over Time Comparison")
        plt.xlabel("Years")
        plt.ylabel("Amount ($)")
        plt.grid(True)
        plt.legend()

        img = io.BytesIO()
        plt.savefig(img, format='png')
        img.seek(0)
        plot_url = base64.b64encode(img.getvalue()).decode()

        return render_template('result.html', final_amount=final_amount_with_interest, difference=difference, plot_url=plot_url)

    else:
        return render_template('index.html')
    


if __name__ == '__main__':
    app.run(debug=True)