https://blog.csdn.net/u013019431/article/details/80776662 在jupyter notebook import pyspark
https://www.douban.com/note/504421303/ 如何初始化
https://blog.csdn.net/dream_an/article/details/51935530 只能创建一次SparkContext引发的错误，所以在前面加个 try sc.stop()
https://www.iteblog.com/archives/1240.html sortBy() sortByKey()
