我正在用熊貓寫一個銀行存款賬戶的模擬。我被復利困住了（這是利息再投資的結果，所以下一個時期的利息是通過本金加上以前累積的利息來賺取的。）到目前為止，我有以下代碼：import pandas as pdfrom pandas.tseries.offsets import MonthEndfrom datetime import datetime# Create a date rangestart = '21/11/2017'now = datetime.now()date_rng = pd.date_range(start=start, end=now, freq='d')# Create an example data frame with the timestamp datadf = pd.DataFrame(date_rng, columns=['Date'])# Add column (EndOfMonth) - shows the last day of the current monthdf['LastDayOfMonth'] = pd.to_datetime(df['Date']) + MonthEnd(0)# Add columns for interest, Sasha, Artem, Total, Descriptiondf['Debit'] = 0df['Credit'] = 0df['Total'] = 0df['Description'] = ''# Iterate through the DataFrame to set "IsItLastDay" valuefor i in df:    df['IsItLastDay'] = (df['LastDayOfMonth'] == df['Date'])# Add the transaction of the first depositdf.loc[df.Date == '2017-11-21', ['Debit', 'Description']] = 10000, "First deposit"# Calculate the principal sum (It the summ of all deposits minus all withdrows plus all compaund interests)df['Total'] = (df.Debit - df.Credit).cumsum()# Calculate interest per day and Cumulative interest# 11% is the interest rate per yeardf['InterestPerDay'] = (df['Total'] * 0.11) / 365df['InterestCumulative'] = ((df['Total'] * 0.11) / 365).cumsum()# Change the order of columnsdf = df[['Date', 'LastDayOfMonth', 'IsItLastDay', 'InterestPerDay', 'InterestCumulative', 'Debit', 'Credit', 'Total', 'Description']]df.to_excel("results.xlsx")輸出文件看起來不錯，但我需要以下內容：“InterestCumulative”欄在每個月的最后一天添加到“Total”欄（復合利息）在每個月的開始，“InterestCumulative”列應該被清除（因為利息被添加到本金總和中）。我怎樣才能做到這一點？