Tokenization of data in dataframe in python
You can try with this:

import pandas as pd
import nltk

df = pd.DataFrame({'frases': ['Do not let the day end without having grown a little,', 'without having been happy, without having increased your dreams', 'Do not let yourself be overcomed by discouragement.','We are passion-full beings.']})

df['tokenized'] = df.apply(lambda row: nltk.word_tokenize(row['frases']), axis=1)