why a python function still returns "None" though i am explicitly returning a value?

Question

def binarySearch(nums,low,high,target):

    if low<=high:
        mid=(low+high)//2

        if nums[mid]==target:
            return mid
        if nums[mid]<target:
            binarySearch(nums,mid+1,high,target)
        else:
            binarySearch(nums,low,mid-1,target)
    else:
        return -1

def search(nums, target):
    return binarySearch(nums,0,len(nums)-1,target)
    

nums=[-1,0,3,5,9,12]
target=9

print(search(nums,target))

console output

Expected output of the above python code for binary search is ‘4’. But my output is ‘None’. I also printed the value of mid on console output just before the line "return mid"(line number 7), it was showing the expected value ‘4’. But it returns ‘None’ instead of that expected value. Please find out the problem and it’s solution.

Asked By: Wreetbhas Pal

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Source

Answer 1

  if nums[mid]<target:
            return binarySearch(nums,mid+1,high,target)
        else:
            return binarySearch(nums,low,mid-1,target)

Answered By: pythonHua

why a python function still returns "None" though i am explicitly returning a value?

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