# Performance note: I benchmarked this code using a set instead of

# a list for the stopwords and was surprised to find that the list

# performed /better/ than the set - maybe because it's only a small

# list.

stopwords = '''

i

a

an

are

as

at

be

by

for

from

how

in

is

it

of

on

or

that

the

this

to

was

what

when

where

'''.split()

def strip_stopwords(sentence):

    "Removes stopwords - also normalizes whitespace"

    words = sentence.split()

    sentence = []

    for word in words:

        if word.lower() not in stopwords:

            sentence.append(word)

    return ' '.join(sentence)