Understanding for loop with xlwt

Question

enter image description hereI would like to perform a calculation with XLWT I'm new to coding and bit confused with using for loop to repeat the formula in following columns, please help me understanding the for loop function for the below calculation

Please refer the image, I need a for loop to fill rest of the columns, so that I do not have to type 'w_sheet.write(1,2,xlwt.Formula('A2-B2'))' multiple times

import xlrd
import xlwt
from xlutils.copy import copy

wb = xlrd.open_workbook('Subtract.xls')
rb = copy(rb)
w_sheet = wb.get_sheet(0)
w_sheet.write(1,2,xlwt.Formula('A2-B2'))
w_sheet.write(2,2,xlwt.Formula('A3-B3'))
w_sheet.write(3,2,xlwt.Formula('A4-B4'))
w_sheet.write(4,2,xlwt.Formula('A4-B4'))

wb.save('Subtract.xls')

Answer 1

Hi try and understand that :D

import xlrd
import xlwt
from xlutils.copy import copy
import os

file_path = "test.xls"

rb = xlrd.open_workbook(file_path, formatting_info=True)
wb = copy(rb)
w_sheet = wb.get_sheet(0)
# For each sheet, do operation
for sheet in rb.sheets():
    # For each row in actual sheet, row += 1 at each operation
    for row in range(sheet.nrows - 1):
        # Set index for operation and result
        index = row + 2
        # Create operation
        operation = 'A' + str(index) + '-B' + str(index)
        # Use operation
        w_sheet.write(index-1, 2, xlwt.Formula(operation))
        # Print for you can understand what it do
        print ("index = " + str(index) + "  operation = " + operation)
# Save in file_path.out.xls
wb.save(file_path + '.out' + os.path.splitext(file_path)[-1])