import numpy as np
import pandas as pd
import pandas_datareader as web

df = web.DataReader('CVX', 'yahoo', '02-15-2015', '11-01-2021')

def save_stock_data_csv(portfolio, start_date, end_date, path):
    '''Download the stock price data of all tickers in a portfolio
    portfolio is a list of strings'''
    
    for ticker in portfolio:
        df = web.DataReader(ticker, 'yahoo', start_date, end_date)
        df.to_csv(path + ticker + '.csv')

path = 'Data/'
portfolio = ['AMZN', 'AAPL']
start_date = '2016-01-01'
end_date = '2020-01-01'

save_stock_data_csv(portfolio, start_date, end_date, path)

portfolio = ['AMZN', 'AAPL']
df = pd.read_csv(path + portfolio[0] + '.csv')
print(df)