Python DataFrameに数字を1から追加したいならこれを使え!

GOOG["Number"] = [i+1 for i in range(len(GOOG))]

import numpy as np

import pandas as pd

from pandas import Series, DataFrame

import pandas_datareader as pdr

from pandas_datareader import DataReader

import matplotlib.pyplot as plt

from datetime import datetime

import seaborn as sns

#リストを作成
gafa_list=["GOOG","AAPL","FB","AMZN"]

#現在
end = datetime.now()
end_year = end.year

#始まり
start = datetime(end.year-10,end.month,end.day)
stare_year = start.year

for gafa_stock in gafa_list:
    globals()[gafa_stock] = pdr.DataReader(gafa_stock, "yahoo", stare_year, end_year)


GOOG["Number"] = [i+1 for i in range(len(GOOG))]

#実行
GOOG.head()