import re


def tokenize(sent):
    """
    Return the tokens of a sentence including punctuation.
    >> tokenize('Bob dropped the apple. Where is the apple?')
        ['Bob', 'dropped', 'the', 'apple', '.', 'Where', 'is', 'the', 'apple', '?']
    >> tokenize('I don't know')
        ['I', 'don', '\'', 'know']
    """
    return [x.strip() for x in re.split("(\W+)", sent) if x.strip()]