Python中如何按值变化对列表元素分组？含连续同值分组需求

原始消息类型列表 #

msg_type = ["sent-message", "received-message", "received-message", "sent-message", "received-message", "sent-message", "received-message", "received-message", "sent-message", "sent-message", "received-message", "sent-message", "sent-message", "received-message", "sent-message", "sent-message", "received-message", "sent-message", "received-message", "received-message", "sent-message", "sent-message", "received-message", "sent-message", "received-message", "sent-message", "received-message"]

分组需求 #

需要将列表按对话交互逻辑分组：

• 连续相同类型的消息归为同一子组
• 连续的sent-message视为一个整体，与后续连续的received-message（同样视为整体）组成一次完整对话交互
• 最终期望得到的分组索引结果：

conversations = [(0,2), (3,4),(5,7),(8,10), (11,13), (14,16),(17,19),(20,22),(23,24),(25,26)]

实现代码 #

msg_type = ["sent-message", "received-message", "received-message", "sent-message", "received-message", "sent-message", "received-message", "received-message", "sent-message", "sent-message", "received-message", "sent-message", "sent-message", "received-message", "sent-message", "sent-message", "received-message", "sent-message", "received-message", "received-message", "sent-message", "sent-message", "received-message", "sent-message", "received-message", "sent-message", "received-message"]

conversations = []
if msg_type:
    # 第一步：按连续相同类型预分组，记录每个子组的起止索引
    pre_groups = []
    start_idx = 0
    current_type = msg_type[0]
    for idx in range(1, len(msg_type)):
        if msg_type[idx] != current_type:
            pre_groups.append((start_idx, idx - 1))
            start_idx = idx
            current_type = msg_type[idx]
    pre_groups.append((start_idx, len(msg_type) - 1))

    # 第二步：合并成对话交互组
    idx = 0
    while idx < len(pre_groups):
        # 遇到sent组，尝试合并后续的received组
        if msg_type[pre_groups[idx][0]] == "sent-message":
            if idx + 1 < len(pre_groups) and msg_type[pre_groups[idx+1][0]] == "received-message":
                conv_start = pre_groups[idx][0]
                conv_end = pre_groups[idx+1][1]
                conversations.append((conv_start, conv_end))
                idx += 2
            else:
                # 处理末尾仅存sent组的边界情况
                conversations.append(pre_groups[idx])
                idx += 1
        else:
            # 处理开头为received组的边界情况
            conversations.append(pre_groups[idx])
            idx += 1

print(conversations)

逻辑说明 #

1. 预分组阶段：遍历列表，将连续相同类型的消息拆分独立子组，记录每个子组的起止索引，为后续合并做准备。
2. 对话合并阶段：遍历预分组结果，将sent-message子组与紧随其后的received-message子组合并为一个对话交互组，完全匹配需求中的分组规则。

内容的提问来源于stack exchange，提问作者Sanket Wagh