import openpyxl as xl

wb = xl.load_workbook('111.xlsx')
sheet = wb['Sheet1']
# cell = sheet['a1']
# cell = sheet.cell(1,1)
# print(cell.value)
# print(f'rows: {sheet.max_row}')

for row in range(2,sheet.max_row + 1):
    cell = (sheet.cell(row,3))
    corrected_price = cell.value * 0.9 
    corrected_price_cell = sheet.cell(row, 4)
    corrected_price_cell.value = corrected_price

wb.save('222.xlsx')

# wb = xl.workbook()
# ws1 = wb.create_sheet("Mysheet") 
# ws.title = "Sherry"
# print(wb.sheetnames)
# only for test





