main_list = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h']
 
result_list = []
for i in range(0, len(main_list), 4):
    item = main_list[i:i+4] # Делаем слайс в 4 элемента
    item = ' (s) '.join(item) + ' (s)' # Объединяем его в строку c разделителями
    result_list.append(item)
 
print(result_list)
 
 
# То же самое, но в одну строку
result_list = [' (s) '.join(main_list[i:i+4]) + ' (s)' for i in range(0, len(main_list), 4)]
print(result_list)

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