Python 如何将字符串转换为数字以粘贴到excel中？

我想写一个程序，将数组的每个元素（用逗号分隔）粘贴到excel的不同列中。我的代码可以工作，但数字存储为文本而不是数字。我怎样才能修好它

from xlwt import Workbook
wb = Workbook()
sheet1 = wb.add_sheet('Sheet 1')

my_string = ["aaaaa,123,532","bbbbb,345,678"]
tab=[]
for y in my_string:
    z=y.split(",")
    tab.append(z)

for a in range(0,len(tab)):
    for b in range(0,len(tab[a])):
        print (tab[a][b])
        sheet1.write(a,b,tab[a][b])

wb.save('exxa.xls')

---

将字符串转换为数字：

my_string = ["aaaaa,123,532","bbbbb,345,678"]
tab=[]
for y in my_string:
    z=y.split(",")
    z[1] = int(z[1])
    z[2] = int(z[2])
    tab.append(z)