pandas中的Concat 2列-AttributeError:“DataFrame”对象没有属性“Concat”

我试着在《熊猫》的两个专栏中进行讨论。代码:

import pandas as pd
import numpy as np
from statsmodels import api as sm
import pandas_datareader.data as web
import datetime

start = datetime.datetime(2015,2,12)
end = datetime.datetime.today()
df = web.get_data_yahoo(['F', '^GSPC'], start, end)

df1 = df.concat(columns=[F['Close'], gspc['Close']], axis=1)

但我得到了以下错误:

AttributeError: 'DataFrame' object has no attribute 'concat'