convert from xls to xlsx using xlrd and openpyxl found at http://stackoverflow.com/questions/9918646/how-to-convert-xls-to-xlsx

open_xls_as_xlsx.py

import xlrd
from openpyxl.workbook import Workbook
from openpyxl.reader.excel import load_workbook, InvalidFileException

def open_xls_as_xlsx(filename):
    # first open using xlrd
    book = xlrd.open_workbook(filename)
    index = 0
    nrows, ncols = 0, 0
    while nrows * ncols == 0:
        sheet = book.sheet_by_index(index)
        nrows = sheet.nrows
        ncols = sheet.ncols
        index += 1

    # prepare a xlsx sheet
    book1 = Workbook()
    sheet1 = book1.get_active_sheet()

    for row in xrange(0, nrows):
        for col in xrange(0, ncols):
            sheet1.cell(row=row, column=col).value = sheet.cell_value(row, col)

    return book1

I try to improve converting performance, see the comment: http://stackoverflow.com/a/42574983/7652407

Since openpyxl 2.5, use book.active instead of book.get_active_sheet(). Workbook.get_active_sheet() was deprecated in 2.3.0 version.