def add_menus_from_file(self, filename):
read_xls = xlrd.open_workbook(filename, formatting_info=True)
for sheet_index in range(read_xls._all_sheets_count):
sheet = Sheet(read_xls.sheet_by_index(sheet_index))
try:
date = sheet.get_menu_date()
products = sheet.get_products()
except IndexError:
raise Exception('Invalid menu format!')
self.menus[date] = products
