import string


def simple(s):
    """Break str `s` into a list of str.

    1. `s` has all of its peripheral whitespace removed.
    1. `s` is downcased with `lower`.
    2. `s` is split on whitespace.
    3. For each token, any peripheral punctuation on it is stripped
       off. Punctuation is here defined by `string.punctuation`.

    Parameters
    ----------
    s : str
        The string to tokenize.

    Returns
    -------
    list of str

    """
    punct = string.punctuation
    final_toks = []
    toks = s.lower().strip().split()
    for w in toks:
        final_toks.append(w.strip(punct))
    return final_toks