binarysearch.py

# Returns index of x in arr if present, else -1 
# arr is the sorted array that is passed in the function
# x is the element we are searching for,
# l is the leftmost element and r the rightmost.
def binarySearch(arr, l, r, x): 
    # Check base case 
    if r >= l: 
        mid = l + (r - l) // 2

        # If element is present at the middle itself 
        if arr[mid] == x: 
            return mid 
        
        # If element is smaller than mid, then it 
        # can only be present in left subarray 
        elif arr[mid] > x: 
            return binarySearch(arr, l, mid-1, x) 

        # Else the element can only be present 
        # in right subarray 
        else: 
            return binarySearch(arr, mid + 1, r, x) 

    else: 
        # Element is not present in the array 
        return -1

# Driver Code 
arr = [ 2, 3, 4, 10, 40 ] 
x = 10

# Function call 
result = binarySearch(arr, 0, len(arr)-1, x) 

if result != -1: 
    print ("Element is present at index % d" % result) 
else: 
    print ("Element is not present in array")