how to get stock data in a csv files
#import external pandas_datareader library with alias of web
import pandas_datareader as web
#import datetime internal datetime module
#datetime is a Python module
import datetime
#datetime.datetime is a data type within the datetime module
start = datetime.datetime(2017, 9, 1)
end = datetime.datetime(2017, 12, 31)
#DataReader method name is case sensitive
df = web.DataReader("nvda", 'yahoo', start, end)
#invoke to_csv for df dataframe object from
#DataReader method in the pandas_datareader library
#..\first_yahoo_prices_to_csv_demo.csv must not
#be open in another app, such as Excel
df.to_csv('first_yahoo_prices_volumes_to_csv_demo.csv')