统计列表中元素出现次数的实用指南-小浪学习网

统计列表中元素出现次数的实用指南

本文旨在提供一个清晰简洁的指南，介绍如何使用python中的Counter对象统计列表中各个元素的出现次数，并按照出现频率进行排序，最终以易于阅读的格式输出结果。通过本文，你将掌握一种高效且Pythonic的方法来处理列表中的数据统计问题。

使用 Counter 统计元素出现次数

Python的 collections 模块提供了一个名为 Counter 的类，它专门用于统计可哈希对象的出现次数。 Counter 对象是一个字典的子类，它的键是元素，值是它们的计数。

基本用法：

导入 Counter 类：
```
from collections import Counter
```
创建 Counter 对象：

将你的列表传递给 Counter 的构造函数。
```
sample_list = ["a", "ab", "a", "abc", "ab", "ab"] element_counts = Counter(sample_list) print(element_counts)
```
输出：
```
Counter({'ab': 3, 'a': 2, 'abc': 1})
```
可以看到，Counter 对象已经统计了列表中每个字符串的出现次数。

示例：统计数字列表的出现次数并排序

假设我们有一个包含数字的列表，我们想要统计每个数字的出现次数，并按照从多到少的顺序输出。

from collections import Counter  numbers = [28, 29, 31, 37, 50, 14, 28, 31, 47, 50, 9, 16, 27, 41, 45, 7, 14, 34, 41, 49, 6, 11, 16, 35, 44, 1, 12, 15, 31, 47, 9, 16, 17, 27, 31, 4, 9, 29, 34, 37, 20, 21, 30, 41, 43, 1, 7, 17, 44, 50, 10, 15, 25, 37, 46, 3, 10, 20, 36, 42, 1, 2, 6, 14, 45, 5, 12, 15, 21, 39, 13, 20, 34, 38, 43, 1, 5, 12, 18, 20, 6, 20, 27, 38, 49, 1, 18, 37, 46, 48, 4, 11, 12, 16, 42, 6, 17, 22, 39, 46, 9, 16, 32, 34, 48, 5, 18, 21, 29, 45, 8, 13, 16, 44, 47, 6, 21, 23, 26, 43, 6, 12, 36, 37, 44, 10, 11, 31, 37, 44, 1, 15, 19, 24, 33, 16, 28, 32, 36, 48, 5, 19, 33, 37, 42, 7, 11, 20, 21, 29, 16, 28, 31, 35, 42, 5, 13, 16, 41, 45, 12, 21, 24, 28, 40, 4, 8, 9, 30, 35, 11, 12, 13, 23, 26, 17, 18, 30, 33, 35, 6, 11, 29, 34, 39, 10, 27, 30, 32, 34, 28, 30, 31, 45, 46, 1, 5, 8, 20, 35, 1, 2, 11, 14, 36, 1, 3, 29, 45, 47, 2, 8, 16, 21, 39, 8, 9, 11, 13, 50, 5, 7, 21, 22, 29, 8, 13, 24, 35, 46, 11, 29, 32, 46, 47, 5, 19, 33, 36, 42, 9, 18, 30, 34, 48, 2, 3, 18, 23, 39, 7, 10, 13, 34, 47, 3, 14, 23, 41, 43, 19, 21, 23, 36, 39, 9, 18, 20, 40, 41, 11, 15, 17, 24, 46, 2, 4, 12, 31, 50, 14, 16, 24, 40, 43, 7, 16, 22, 38, 41, 3, 9, 11, 20, 39, 10, 16, 34, 36, 49, 2, 9, 38, 40, 44, 3, 17, 19, 32, 38, 6, 12, 25, 31, 37, 1, 35, 36, 38, 39, 12, 21, 23, 26, 41, 2, 16, 22, 28, 46, 8, 40, 41, 46, 47, 2, 5, 11, 27, 38, 14, 18, 20, 39, 42, 1, 13, 16, 23, 27, 9, 11, 13, 15, 25, 21, 29, 31, 46, 49, 5, 13, 43, 45, 50, 3, 8, 10, 31, 36, 8, 18, 26, 38, 39, 14, 24, 31, 44, 45, 23, 24, 38, 42, 44, 14, 24, 29, 45, 48, 13, 28, 29, 31, 47, 17, 18, 40, 43, 50, 7, 8, 12, 21, 43, 16, 23, 30, 37, 41, 6, 8, 42, 49, 50, 11, 16, 22, 34, 46, 5, 14, 35, 40, 47, 6, 15, 21, 34, 48, 6, 21, 23, 31, 39, 26, 36, 43, 47, 49, 1, 17, 22, 29, 31, 9, 30, 34, 38, 48, 4, 14, 15, 20, 28, 9, 20, 21, 22, 38]  # 使用 Counter 统计数字出现次数 number_counts = Counter(numbers)  # 按照出现次数从多到少排序 sorted_counts = number_counts.most_common()  # 打印结果 for number, count in sorted_counts:     print(f"{number}:{count}x")

代码解释：

Counter(numbers) 创建一个 Counter 对象，统计 numbers 列表中每个数字的出现次数。
number_counts.most_common() 返回一个列表，其中包含按照出现次数从多到少排序的 (元素, 计数) 元组。
循环遍历排序后的列表，并使用 f-String 格式化输出每个数字及其出现次数。

注意事项

Counter 对象只能用于统计可哈希的对象（例如，字符串、数字、元组）。不能直接统计列表的列表，因为列表是不可哈希的。
Counter 对象的键是元素，值是它们的计数。你可以像访问字典一样访问 Counter 对象的值。
most_common() 方法返回一个列表，其中包含按照出现次数从多到少排序的 (元素, 计数) 元组。如果只想获取出现次数最多的前 N 个元素，可以传递一个整数给 most_common() 方法，例如 most_common(5)。