hello

[vcbeaut]

handsome boy, excuse me!
when I have been studing chatbot, I have a question that I don't understand . because of I thank you are enthusiastic,so I want to ask you for this question as follow:

eng_vocab_size = len(eng_tokenizer.word_index) + 1

this code means vocabulary size equals the length of word-index adding 1, I dont't understand why it need to add 1. I think it is necessary to add 1. please you help me , thank you !