Saving excel work book not working in python

for sheet_name in book.sheet_names():   
for index in range(len(tabs)):
tab = tabs[index]
    if sheet_name == tab:       
        dump_file_name = dump_files[index]
        dump_file_name = file_prefix+dump_file_name
        sheet = book.sheet_by_name(sheet_name)

        new_book = Workbook()
        sheet1 = new_book.add_sheet("Sheet 1")          

        for row in range(sheet.nrows):
            values = []
            for col in range(sheet.ncols):

                sheet1.write(row,col,sheet.cell(row,col).value)


        xlsx_file_name = dirname+"/"+dump_file_name+".xlsx"
        sheet1.title = xlsx_file_name           
        new_book.save(xlsx_file_name)

file is creating and data is there but if i open it in open offcie org and click save button it asking for new name. The file can not be read by PHP also