从tushare pro获取上证指数内成分股权重排序分出等级

import tushare as ts
import pandas as pd
import numpy as np
import datetime
from dateutil.relativedelta import relativedelta

today = datetime.datetime.today().strftime('%Y%m%d')    #获取今天的年月日
last_mon = datetime.datetime.today() - relativedelta(months=1)   #获取前一月的日期
last_mon = last_mon.strftime('%Y%m%d')   # 转换成STR

ts.set_token('you token')
pro=ts.pro_api()

df = pro.index