sandwich_combinations.py

# list of lists, length is not capped
options = [
    ["Italian", "9-Grain Wheat"], # Bread
    ["American", "Swiss", "Cheddar"],        # Cheese
    ["Ranch", "Mayo", "BBQ", "Ketchup", "Thousand Island"],            # Sauce
    ["Honey Mustard", "Plain"]    # Ham
]

def multiply_list(options, results_input=[]):
    # base case
    if len(options) == 0:
        return results_input

    # temp list
    resulting_list = []

    # loop through options in first list
    for i in options.pop(0):
        # if first iteration, init list of lists
        if results_input == []:
            resulting_list.append([i])

        # otherwise start appending
        else:
            # for each combination already made, add next layer
            for j in results_input:
                resulting_list.append(j + [i])

    # repeat (WAH RECURSION)
    return multiply_list(options, resulting_list)

multiply_list(options)