import pandas as pd
import datetime

dataset = pd.read_csv("turnover.csv")

turnover = [0.0]

dataset = dataset.fillna(0)

for i in range(len(dataset)-1):
    if dataset.iloc[i, 0] == dataset.iloc[i+1, 0]:
        calcualted_turnover = float(dataset.iloc[i+1, 3]) - float(dataset.iloc[i, 3])
    else:
        if datetime.datetime.strptime(dataset.iloc[i+1, 2], "%d/%m/%Y") >= datetime.datetime(year=2018, month=1, day=1):
            calcualted_turnover = dataset.iloc[i+1, 3]
        else:
            calcualted_turnover = 0
    turnover.append(calcualted_turnover)
    if dataset.iloc[i, 1][7:] == "R":
        new_code = dataset.iloc[i, 1][:7] + "0"
        dataset.replace([i, 1], new_code, inplace=True, regex=True)

dataset["turnover"] = turnover

dataset.to_csv('turnover_complete.csv', index=False)