python计算月份差

from datetime import datetime
a = "20220308"
b = "20211001"
aa = datetime.strptime(a[:4]+"-"+a[4:6]+"-"+a[6:],"%Y-%m-%d")
bb = datetime.strptime(b[:4]+"-"+b[4:6]+"-"+b[6:],"%Y-%m-%d")
def month_delta(start_date, end_date):
    flag = True
    if start_date > end_date:
        start_date, end_date = end_date, start_date
        flag = False
    year_diff = end_date.year - start_date.year
    end_month = year_diff * 12 + end_date.month
    delta = end_month - start_date.month
    return -delta if flag is False else delta

print("---",month_delta(bb,aa))