Print out all combinations of k numbers out of 1...N

e.g. when k = 2, n = 4
Print out 12, 13, 14, 23, 24, 34

def combi (k,arr):
        if k == 1:
                return [[i] for i in arr]
        elif k == 0 or len(arr) == 0:
                return []

        L = []
        for i in range (0,len(arr)):
                arr2 = arr[:]
                arr2.remove(arr[i])
                for v in  combi (k-1 , arr2):
                        L.append( [arr[i]] + v )

        return L

print combi ( 2 , range(1,4) ) 
 

One limitation with this function is that it returns 14 but also 41
The following code solves this problem

def combi2 (k,arr):
        if k == 1:
                return [[i] for i in arr]
        elif k == 0 or len(arr) == 0:
                return []

        L = []
        arr2 = arr[:]
        while len(arr2) > 0:
                val = arr2.pop(0)

                for v in  combi (k-1 , arr2):
                        L.append( [val] + v )

        return L