python nltk tokenize

>>> import nltk
>>> sentence = """At eight o'clock on Thursday morning
... Arthur didn't feel very good."""
>>> tokens = nltk.word_tokenize(sentence)
>>> tokens
['At', 'eight', "o'clock", 'on', 'Thursday', 'morning',
'Arthur', 'did', "n't", 'feel', 'very', 'good', '.']

Here is what the above code is Doing:
1. Importing the NLTK library.
2. Creating a sentence.
3. Tokenizing the sentence into words.
4. Printing out the words.