With this patch it is possible to use a Workbook.Workbook.save() method not only with the file name as argument, but with the file object too. For example (Django-related code):
w = Workbook()
response = HttpResponse(mimetype='application/vnd.ms-excel')
response['Content-Disposition'] = 'attachment; filename=%s' % file_name
In this example, "response" object isn`t a string, but is supports a "write" method as file object.