Binary_search.py

# Returns index of x in arr if present, else -1 
def binary_search(arr, low, high, x): 
  
    # Check base case 
    if high >= low: 
  
        mid = (high + low) // 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 binary_search(arr, low, mid - 1, x) 
  
        # Else the element can only be present in right subarray 
        else: 
            return binary_search(arr, mid + 1, high, x) 
  
    else: 
        # Element is not present in the array 
        return -1
  
# Test array 
arr = [ 2, 3, 4, 10, 40 ] 
x = 10
  
# Function call 
result = binary_search(arr, 0, len(arr)-1, x) 
  
if result != -1: 
    print("Element is present at index", str(result)) 
else: 
    print("Element is not present in array")