main.py

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

r = 0.03
cash_flow = pd.DataFrame({'Year': [1, 2, 3, 4, 5, 6],
  'Cash': [200, 200, 200, 200, 200, 200]})
# PV (Present Value) = Cash (at period 1) / (1 + r)^n
cash_flow['PV'] = cash_flow['Cash'] / (1.0 + r) ** cash_flow['Year']
npv = cash_flow['PV'].sum()
print(round(cash_flow))