Python: All Possible Combinations

combinations.py

def combinations(n, list, combos=[]):
    # initialize combos during the first pass through
    if combos is None:
        combos = []

    if len(list) == n:
        # when list has been dwindeled down to size n
        # check to see if the combo has already been found
        # if not, add it to our list
        if combos.count(list) == 0:
            combos.append(list)
            combos.sort()
        return combos
    else:
        # for each item in our list, make a recursive
        # call to find all possible combos of it and
        # the remaining items
        for i in range(len(list)):
            refined_list = list[:i] + list[i+1:]
            combos = combinations(n, refined_list, combos)
        return combos