Python astype function usage analysis

My database looks like this

framework

I took one of the name age nr, made array, as long as the data taken by the existence of str type, then take out the data, all converted to str type, that is, array array elements are all str, regardless of the database definition is not int type.

Then the problem comes, the data removed into the formula for the calculation of the time, it will not match the type, this is used asype()

The code is as follows

import pymysql
import numpy as np

conn = (host='39.106.168.84', user='xxxxxx', password='xxxxxx', port=3306,
            db='flask_topvj_net')
cur = ()
sql = "SELECT `name`, `age`,`nr` FROM `student` WHERE 1"
(sql)
u = ()
u=(u)
()
print(u)

#a=u[:,1]*5
#b=u[:,2]*5# Error Demonstration

a=u[:,1].astype()*5
b=u[:,2].astype()*5
print(a)
print(b)

in the end

You can see that the second and third columns of the array are multiplied by 5. The calculation was successful.

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