Merge sort pretty printing

import math

def merge_sort(unsorted, max_iterations=None, level=1):
    """Performs a merge sort on an input list of numbers/characters"""
    curr_entry = [[0, unsorted]] if not max_iterations else []
    max_iterations = max_iterations or math.ceil(math.log2(len(unsorted))) * 2

    mid = len(unsorted) // 2
    old_left = unsorted[:mid]
    old_right = unsorted[mid:]

    left_progress = merge_sort(old_left, max_iterations, level + 1) if len(old_left) > 1 else [old_left, []]
    right_progress = merge_sort(old_right, max_iterations, level + 1) if len(old_right) > 1 else [old_right, []]

    left = left_progress[0]
    right = right_progress[0]

    curr_entry += [[level, old_left, old_right], [max_iterations - level, list(left), list(right)]]

    reversed_sorted = [
        left.pop()
        if left and (
            not right
            or left[len(left) - 1] > right[len(right) - 1]
        ) else right.pop()
        for i in range(len(unsorted))
    ]

    return [reversed_sorted[::-1], left_progress[1] + right_progress[1] + curr_entry]

def pretty_print(raw_progress):
    layers = []
    for state in raw_progress[1]:
        level = state[0]
        while level >= len(layers):
            layers.append([])
        for data in state[1:]:
            if data:
                layers[level].append(data)
    layers.append([raw_progress[0]])
    return '\n'.join([''.join([str(entry) for entry in level]) for level in layers])


ran_list = [23,5,6,8,812,4,124,3,7,1,12,5,85,0,24,87,34,242,213,566,21,7,2143,635,573,243,548,89,456]
progress = merge_sort(ran_list)
print(pretty_print(progress))