Python如何对列表元素分组统计出现次数并按指定格式输出

完整可运行代码（依赖内置标准库） #

from collections import defaultdict

a = ['426::1898','426::1898','426::1900','425::1898']
# 初始化嵌套统计结构：外层key为拆分后的后缀，内层key为前缀，值为对应出现次数
stat = defaultdict(lambda: defaultdict(int))

for item in a:
    prefix, suffix = item.split('::')
    stat[suffix][prefix] += 1

# 按要求格式输出
for suffix, prefix_count in stat.items():
    parts = [f"{prefix} {cnt} times" for prefix, cnt in prefix_count.items()]
    print(f"{suffix}: {', '.join(parts)}")

运行输出结果 #

1898: 426 2 times, 425 1 times
1900: 426 1 times

无额外导入的原生实现版本 #

如果不想引入collections依赖，可以用普通字典实现，效果完全一致：

a = ['426::1898','426::1898','426::1900','425::1898']
stat = {}

for item in a:
    prefix, suffix = item.split('::')
    if suffix not in stat:
        stat[suffix] = {}
    if prefix not in stat[suffix]:
        stat[suffix][prefix] = 0
    stat[suffix][prefix] += 1

for suffix, prefix_count in stat.items():
    parts = [f"{prefix} {cnt} times" for prefix, cnt in prefix_count.items()]
    print(f"{suffix}: {', '.join(parts)}")

内容的提问来源于stack exchange，提问作者Miguelii