Question

假设我有以下Python列表：

mylist = [
    ["name_a", "sex_male", "age_15", "grade_11"],
    ["name_b", "sex_male", "age_18", "grade_9"],
    ["name_c", "sex_male", "age_11", "grade_8"],
    ["name_d", "sex_male", "age_16", "grade_12"],
    ["name_e", "sex_male", "age_19", "grade_13"],
]

我想调用Python的sort（）函数，按年龄

对 mylist 进行排序

例如，我想做这样的事情：

mylist.sort(key=...)

获取输出

mylist = [
    ["name_c", "sex_male", "age_11", "grade_8"],
    ["name_a", "sex_male", "age_15", "grade_11"],
    ["name_d", "sex_male", "age_16", "grade_12"],
    ["name_b", "sex_male", "age_18", "grade_9"],
    ["name_e", "sex_male", "age_19", "grade_13"],
]

这样做的正确方法是什么？

P.S

还有一个问题：为什么在Python的sort（）函数中使用排序算法？（例如QuickSort？）

Answer 1

def extract_age(item):
    """age is stored in the 3rd element of item. eg.
      ['name_c', 'sex_male', 'age_11', 'grade_8']
      and should be returned as an int
    """
    return int(item[2].split('_')[1])

mylist.sort(key=extract_age)

Answer 2

假设所有年龄段看起来都一样：

>>>mylist.sort(key=lambda e: int(e[2].split('_')[1]))
[['name_c', 'sex_male', 'age_11', 'grade_8'],
 ['name_a', 'sex_male', 'age_15', 'grade_11'],
 ['name_d', 'sex_male', 'age_16', 'grade_12'],
 ['name_b', 'sex_male', 'age_18', 'grade_9'],
 ['name_e', 'sex_male', 'age_19', 'grade_13']]

lambda表达式解析年龄字段，方法是在_字符上拆分字符串，然后转换为int拆分第二个元素的结果。

Python使用TimSort算法，这是由Tim Peters创建的Python定制搜索算法。

Python：按字符串元素排序列表列表

2 个答案: