is:issue how to sum string type load from csv? and how to convert string column to timestamp?

[xkungfu]

my csv file column fields: date, username, vol, type

all fields are string fromat.

can't load as double, but when load as string,

I can't sum vol column, and can't select rows by date range.

how to convert string column to int or double?

and how to convert string column to timestamp?

PS: why I can't find any doc and issue about my question? why others didn't have this issue?

thanks!

[xkungfu]

my mistake.this is about xtensor ,not python.