Binary search in Python

binary_search.py

def binary_search(sorted_list, target):
    left_pointer = 0
    right_pointer = len(sorted_list)
    
    while left_pointer < right_pointer:
        # calculate the middle index using the two pointers
        mid_idx = (left_pointer + right_pointer) // 2
        mid_val = sorted_list[mid_idx]
        if mid_val == target:
            return mid_idx
        if target < mid_val:
            # set the right_pointer to the appropriate value
            right_pointer = mid_idx
        if target > mid_val:
            # set the left_pointer to the appropriate value
            left_pointer = mid_idx + 1

    return "Value not in list"


# test cases
print(binary_search([5, 6, 7, 8, 9], 9))
print(binary_search([5, 6, 7, 8, 9], 10))
print(binary_search([5, 6, 7, 8, 9], 8))
print(binary_search([5, 6, 7, 8, 9], 4))
print(binary_search([5, 6, 7, 8, 9], 6))