code error summary

1.在循环过程中删除了列表中的元素，导致列表长度变短，索引出错。

english_punctuations = [',','.',':',';','?','(',')','[',']','&','!','*','@','#','$','%','...']

sentence='''@justinbieber Thank u Justin for this amazing'''

line=nltk.word_tokenize(sentence)

foriinrange(len(line)):

ifline[i]=='@':

line[i+1]='name'

ifline[i]=='%':

line[i]='percentage'

ifline[i].isdigit():

line[i]='number'

ifline[i]inenglish_punctuations:

line.pop(i)

iflen(line[i])<2:

line.pop(i)

line[i]=line[i].lower()