Mergesort Algorithm - Python

mergesort.py

def split_leftlist(list):
    half = len(list) / 2
    return list[:half]

def split_rightlist(list):
    half = len(list) / 2
    return list[half:]

def merge(left_list, right_list):
    output_list = []

    leftCounter = 0
    rightCounter = 0

    for count in range(len(left_list) + len(right_list)):
        
        if rightCounter == len(right_list):
            [output_list.append(each) for each in left_list[leftCounter: ]]
            return output_list
        elif leftCounter == len(left_list):
            [output_list.append(each) for each in right_list[rightCounter: ]]
            return output_list
        
        if (left_list[leftCounter] <= right_list[rightCounter]):
            output_list.append(left_list[leftCounter])
            leftCounter += 1
        elif (right_list[rightCounter] <= left_list[leftCounter]):
            output_list.append(right_list[rightCounter])
            rightCounter += 1

    return output_list

def merge_sort(list):
    if len(list) <= 1:
        return list

    left_list = split_leftlist(list) #Recursively split the left part of list
    left_list = merge_sort(left_list)
        
    right_list = split_rightlist(list)
    right_list = merge_sort(right_list) #Recursively split the right part of list
    
    return merge(left_list, right_list)
    

if __name__ == '__main__':
    merge_sort([]) #Enter list goes here