Why I am getting None in place of int from if block inside a method called by another method in the class

Question

Here is the code, I am trying to get a binary search result using a method inside the class. The class has more functions but only this function is giving the wrong output (None in place an integer). The if part from line number 10 to 15 is causing the problem.

class Solution:
    def getNum(self, nums, x):
        L_nums = len(nums)
        j = self.binary_search( nums, 0, L_nums-1, x)
        print("j=",j)
   
   
    def binary_search(self, nums, start, end, x):
        print("BS called  start=>", start,"end=>", end,"x=>", x)
        if end==start:
            if nums[end]==x:
                return end
            else:
                print("called else and returing -1")
                return -1
        i = (end-start)//2 + start
        print("i=",i)
        if x==nums[i]:
            return i
        elif x>nums[i]:
            self.binary_search(nums, i+1, end, x)
        else:
            self.binary_search(nums, start, i-1, x)


sol = Solution()
sol.getNum([1,3,5,7,9],1)

output: here j should be 0, in place of that it is returning None

BS called  start=> 0 end=> 4 x=> 1
i= 2
BS called  start=> 0 end=> 1 x=> 1
i= 0
j= None

Answer 1

Short answer to your question: include the "return" in raw 21,23.

20.    elif x>nums[i]:
    

21.        return self.binary_search(nums, i+1, end, x)
    

22.    else:
    

23.        return self.binary_search(nums, start, i-1, x)