Some more improvements of comments.
Some more improvements of comments.

linan7788626/pandas_tutorial,Sandor-PRA/pandas_tutorial,jonathanrocher/pandas_tutorial,ajaykliyara/pandas_tutorial,Sandor-PRA/pandas_tutorial,wateryhcho/pandas_tutorial,linan7788626/pandas_tutorial,Sandor-PRA/pandas_tutorial,ajaykliyara/pandas_tutorial,jonathanrocher/pandas_tutorial,wateryhcho/pandas_tutorial,wateryhcho/pandas_tutorial,linan7788626/pandas_tutorial,ajaykliyara/pandas_tutorial,jonathanrocher/pandas_tutorial