the odds() problem does return the value of the odd index, on my local machine but on treehouse challenge, not so.

def first_4(x):
    return x[:4]
def first_and_last_4(y):
    first = y[:4]
    last = y[-4:]
    return first + last
def odds(z):
    for i in z:
        index = z.index(i)
        if index % 2 != 0:
            return i

# I realized that the assumptions are the numbers are in descending or ascending order, that are not "messy".
#There fore, works and passed challenge,
#I was wrong in my assumptions, not the calculations. The above works if you dont know where the odd indexes are, if #you were to have list that extend or append lists, the above may be useful.  I made it difficult.  

def odds(z):
    return z[1::2]