Unknown cause for TypeError in Python 2.6

Question

I am writing a program which reads input from a file called 'votes.txt'.

It reads in some line of information, each of which is a 'vote' with parties ordered by preference.

The program needs to take this data, and output the winner of the election.

My Code is as follows:

# Define the count_votes() function
def count_votes(to_count):
    "Count each vote's preference"

    output = []
    for vote in to_count:
        output.append(vote[0])
    return output

# Define the find_lowest() function
def find_lowest(results):
    "Find which party has the least votes"

    to_real = []
    min_ = min(results.values())
    for party in results:
        if results[party] == min_:
            to_real.append(party)
    return to_real

# Define the reallocate() function
def reallocate(results, to_real, votes):
    "Reallocate votes for losing party"

    for party in to_real:
        for vote in votes:
            if vote[0] == party:
                del vote[0]
                results[vote[0]] += 1
                if party in results:
                    del results[party]
            if party in vote:
                del vote[vote.index(party)]
    return results, votes

# Define winner() function to determine if there is an outcome
def winner(results, no_votes):
    if max(results.values()) > (no_votes / 2.0):
        for party in results:
            if max(results.values()) == results[party]:
                return party
    elif max(results.values()) == (no_votes / 2.0):
        output = []
        for party in results:
            if max(results.values()) == results[party]:
                ouput.append(party)
        return party

# Define the post_alloc() function
def post_alloc(results, votes):
    if not winner(results, len(votes)):
        lowers = find_lowest(results)
        results, votes = reallocate(results, lowers, votes)
        results, votes, lowers = post_alloc(results, votes)
    else:
        return results, votes, winner(results, len(votes))

# Define the election() function
def election():
    "Calculate the result of the election"

    # Take file input
    input_file = []
    for line in open('votes.txt', 'rU'):
        input_file.append(line)

    # Create list of votes
    votes = []
    for vote in input_file:
        votes.append(vote.split())

    # Create a results dictionary
    results = {}
    for party in votes[0]:
        results[party] = 0

    # Allocate first preferences
    count_result = count_votes(votes)
    for party in count_result:
        results[party] += 1

    # Continue to reallocate until there is a winner
    win_list = []
    results, votes, win_list = post_alloc(results, votes)

    # Produce result
    if type(win_list) == type(''):
        print win_list, 'won the election.'
    else:
        print win_lit[0], win_list[1], 'tie the election.'

# Carry out program
election()

But I got this error:

>Traceback (most recent call last):  
>    File "do_we_have_a_government.py", line 94, in   
>        election()  
>    File "do_we_have_a_government.py", line 85, in election  
>        results, votes, win_list = post_alloc(results, votes)  
>    File "do_we_have_a_government.py", line 55, in post_alloc  
>        results, votes, lowers = post_alloc(results, votes)  
>TypeError: 'NoneType' object is not iterable  

Thanks for any help!

Answer 1

The call on line 55 to post_alloc(results,votes) returns None. It looks like you're missing a return statement in that function (you have on in the else case, but not the if).