How would I make it so only some items are able to be used at the same time when finding all possible combinations of a list

Question

Sorry for the pretty undescriptive title, this is a pretty weird problem. I'm using this code to find all possible combinations of my list:

from itertools import chain, combinations
def powerset(iterable):
    "powerset([1,2,3]) --> () (1,) (2,) (3,) (1,2) (1,3) (2,3) (1,2,3)"
    s = list(iterable)
    return chain.from_iterable(combinations(s, r) for r in range(len(s)+1))


stuff = ['pretzel', 'sesame', 'sourdough', 'donut', 'waffles', 'beef', 'turkey', 'chicken', 'tuna', 'vegan', 'pork', 'steak', 'bison', 'cheese', 'kethcup', 'mayo', 'pickles', 'mustard', 'lettuce', 'onions', 'tomato', 'bacon', 'bbq', 'hotsauce', 'pb', 'jelly', 'butter', 'jalapeno', 'frenchfry', 'apple', 'honeymustard', 'onionrings', 'ranch', 'macncheese', 'pulledpork', 'avacado', 'mushrooms']
for i, combo in enumerate(powerset(stuff), 1):
    print('combo #{}: {}'.format(i, combo))

To be completely honest with you, this is the first hunk of code I found on Google that did pretty much what I wanted. It spits out all of the possible combinations, and even gives each one a number! However, what I need it to do has changed and I really can't figure out what to do (which isn't really saying much) and so I'm coming here to ask: How would I make it so only some of the items in that list can be used together? For example, I don't want the types of bun or meat to be able to be listed together, but the condiments can be used in any combination (or lack thereof). Thanks in advance.

Edit: What I'm trying to accomplish in the end is that I need to find and list all of the possible combinations of bun, meat, and condiments on a given sandwich. The types of bun and meat in a given option can only be used once, but any combination of any condiments is acceptable (so using them all is an option).

Answer 1

You could do:

def subsets(l):
   ret = []
   for n in range(len(l)+1):
       ret += list(itertools.combinations(l, n))
   return ret

buns = ["sesame", "sourdough"]
meat = ["ham" , "beef"]
condiments = ["ketchup","mustard", "onions"] 
combo = []
for b in buns:
   for m in meat:
       for c in subsets(condiments):
            x = [b,m]
            for s in c:
                x.append(s)
            combo.append(x)

combo would contain all the possible answers