comb.py

# Pop item at index i from list. Returns (item,new_list)
def pop2(l,i):
  l1 = l[0:i]
  l2 = l[(i+1):]
  return (l[i],l1+l2)

def solve(numbers,goal):
  solutions = []
  for i in range(len(numbers)):
    (num,numbers2) = pop2(numbers,i)
    diff = goal - num
    if diff==0:
      solutions.append([num])
    elif diff>0:
      for sol in solve(numbers2,diff):
        solutions.append([num]+sol)
    # diff<0 -> CUT SUBTREE

  return solutions

numbers = [1, 2, 3, 7]
goal = 10

result = solve(numbers,goal)
print result