index    0
0     a       A
1     b       B
2     c       C

words.rename({'index':'word','0':'counts'},axis='columns',inplace=True)

word     0
0     a       A
1     b       B
2     c       C

words['0']

KeyError: '0'

words=df_new['text'].str.split(expand=True).stack().value_counts()
words=pd.DataFrame(words)
words.reset_index(level=0,inplace=True)