Count the number of vowelgroups in a string
Using the itertools recipe pairwise you can directly use sum to calculate the number of vowel groups by iterating over pairs of values.

In addition I would make the vowels a global constant and a set, because building the string every time is going to cost some time. Also, sets have very fast membership testing.

With these changes you would get:

from itertools import tee, izip

VOWELS = set("aeiouy")

def pairwise(iterable):
    """s -&gt; (s0,s1), (s1,s2), (s2, s3), ..."""
    a, b = tee(iterable)
    next(b, None)
    return izip(a, b)

def count_vowelgroups(words):
    words = words.lower()
    return sum(c_1 not in VOWELS and c in VOWELS for c_1, c in pairwise(words))