complicated list return?

[lukerobi]

lets say i have a list:
L = [1,2,3,4,5,6,7,8,9]

x could be anything, but it wont ever be longer than len(L) - 1.. just for what im asking, im setting it to 3
x = 3

value could also be anything, but not exceeding sum(L)
value = 8

What i am trying to figure out is what combinations of items in the list are equal to value, but the length of the combonation cannot exceed x and you cannot use the same item twice.

the anwsers i would want returned are (but not limited to):
[8], [1,7], [2,6], [3,5], [4,4], [1,2,5], [1,3,4], [1,4,3]

You wouldn't return combination of 4 list items because that would exceed x.

Just fyi, this is not homework lol. This is a personal project im working on, and im just stumped.

I wish i had some broken code to post, but i can't even get that far... im not sure how to tackle this since the value of x can be different... if i had to find a static number of list items whos value = 8, i could do that easily... but im lost with this.

My best attempt used L[a:b] changing the values of b and a as b - a approached x and y <= len(L) ... it gave me results, but only if the list items were next to eachother. (8 would not work, but 9 will give you some returns)

Thanks alot for reading the wall of text, and I apreciate any and all anwsers!

[lukerobi]

just something i forgot... the length of L is also subject to change.

[woooee]

The question is not clear, so let us say
if number_list = [1,2,3,4,5,6,7,8,9]
3 = maximum numbers that can be combined
(and single numbers are not included),
then you would use a function to calculate the sum of a group of numbers and return True or False
def return_sum(number_list, compare_to):

and would use a for loop(s) to group the numbers, that is, send groups of 2, 3, etc to the function for comparison. Start with the individual parts. Use a loop to divide the list into groups, send each one to the function, and do something with the result.

[lukerobi]

i ended up figuring this out using itertools.combination

[vegaseat]

If you have time, post the solution you came up with.

[lukerobi]

If you have time, post the solution you came up with.

Sure here you go..

from itertools import cominations

def getCombos(somelist, x):
    x += 1
    for n in range(1,x):
        gen = combinations(somelist,n)
        while True:
            try:
                combo = gen.next()
                yield combo
            except StopIteration:
                break

example of it working:

>>> data = getCombos([1,2,3,4],3)
>>> 
>>> while True:
	try:
		print data.next()
	except StopIteration:
		break

	
(1,)
(2,)
(3,)
(4,)
(1, 2)
(1, 3)
(1, 4)
(2, 3)
(2, 4)
(3, 4)
(1, 2, 3)
(1, 2, 4)
(1, 3, 4)
(2, 3, 4)

[vegaseat]

Missing the value part.

[lukerobi]

Missing the value part.

Yeah i really have not used that yet in my code, although i planed to...

but u could do it like this:

def getCombos(somelist, x):
    x += 1
    for n in range(1,x):
        gen = combinations(somelist,n)
        while True:
            try:
                combo = gen.next()
                if sum(combo) == value:
                    yield combo
            except StopIteration:
                break

it working:

>>> value = 4
>>> data = getCombos([1,2,3,4],2)
>>> data.next()
(4,)
>>> data.next()
(1, 3)