当Index是日期时，迭代数据帧

Question

我想知道是否有迭代dataframe而它的索引是一个日期并获得以前的索引而不使用预设函数，如shift()，rolling()等？

import pandas as pd
import numpy as np
pd.core.common.is_list_like = pd.api.types.is_list_like
from pandas_datareader.data import DataReader 
from datetime import datetime

f = DataReader('F', 'robinhood')

f.head() outout screenShot

for index, row in f.iterrows():
prev = f.loc[index - someNumber] <----- You cant minus from date
current = f.loc[index]