Python - Get list span

def get_list_span(l: list):
    """
    For list ['a', 'a', 'a', 'b', 'c', 'c', 'd', 'd', 'd', 'd'], 
    its span list is [3, 0, 0, 1, 2, 0, 4, 0, 0, 0] .
    :param l: 
    :return: 
    """

    span_list = []
    span = 1
    for i in range(len(l)):
        if i == 0:                            # 第一项span设为1
            span_list.append(1)
        else:
            if l[i] == l[i-span]:             # 与之前项相等，之前项的span值加1，本项span设为0，span值加1
                span_list[i-span] += 1
                span_list.append(0)
                span += 1
            else:                             # 与之前项不等，本项span设为1，span值恢复为1
                span_list.append(1)
                span = 1
    return span_list