pandas 切片索引 https://www.zybuluo.com/jk88876594/note/837142 https://www.yiibai.com/pandas/python_pandas_indexing_and_selecting_data.html

pandas 分组聚合 https://www.jianshu.com/p/4345878fb316

pands merge，join， concate

numpy 数组创建 http://www.zmonster.me/2016/02/25/creation-and-io-of-ndarray.html