Python中按特定键对字典数据进行分组列表

Python中按特定键对字典数据进行分组列表可以使用 itertools.groupby() 方法完成。

Itertools.groupby()

此方法计算 iterable 中存在的每个元素的键。它返回分组项的键和可迭代项。

Syntax: itertools.groupby(iterable, key_func)

Parameters:

• iterable: Iterable can be of any kind (list, tuple, dictionary).
• key_func: A function that calculates keys for each element present in iterable.

Return type: It returns consecutive keys and groups from the iterable. If the key function is not specified or is None, key defaults to an identity function and returns the element unchanged.

让我们看看例子：
示例 1：假设我们有员工和公司字典列表。

INFO = [
    {'employee': 'XYZ_1', 'company': 'ABC_1'},
    {'employee': 'XYZ_2', 'company': 'ABC_2'},
    {'employee': 'XYZ_3', 'company': 'ABC_3'},
    {'employee': 'XYZ_4', 'company': 'ABC_3'},
    {'employee': 'XYZ_5', 'company': 'ABC_2'},
    {'employee': 'XYZ_6', 'company': 'ABC_3'},
    {'employee': 'XYZ_7', 'company': 'ABC_1'},
    {'employee': 'XYZ_8', 'company': 'ABC_2'},
    {'employee': 'XYZ_9', 'company': 'ABC_1'}
]

现在我们需要通过“公司”键名显示所有数据组。

代码：

Python3

# import a groupby() method
# from itertools module
from itertools import groupby
  
# dictionary
INFO = [
    {'employee': 'XYZ_1', 'company': 'ABC_1'},
    {'employee': 'XYZ_2', 'company': 'ABC_2'},
    {'employee': 'XYZ_3', 'company': 'ABC_3'},
    {'employee': 'XYZ_4', 'company': 'ABC_3'},
    {'employee': 'XYZ_5', 'company': 'ABC_2'},
    {'employee': 'XYZ_6', 'company': 'ABC_3'},
    {'employee': 'XYZ_7', 'company': 'ABC_1'},
    {'employee': 'XYZ_8', 'company': 'ABC_2'},
    {'employee': 'XYZ_9', 'company': 'ABC_1'}
]
  
  
# define a fuction for key
def key_func(k):
    return k['company']
  
# sort INFO data by 'company' key.
INFO = sorted(INFO, key=key_func)
  
for key, value in groupby(INFO, key_func):
    print(key)
    print(list(value))

输出：

ABC_1
[{’employee’: ‘XYZ_1’, ‘company’: ‘ABC_1′}, {’employee’: ‘XYZ_7’, ‘company’: ‘ABC_1′}, {’employee’: ‘XYZ_9’, ‘company’: ‘ABC_1′}]
ABC_2
[{’employee’: ‘XYZ_2’, ‘company’: ‘ABC_2′}, {’employee’: ‘XYZ_5’, ‘company’: ‘ABC_2′}, {’employee’: ‘XYZ_8’, ‘company’: ‘ABC_2′}]
ABC_3
[{’employee’: ‘XYZ_3’, ‘company’: ‘ABC_3′}, {’employee’: ‘XYZ_4’, ‘company’: ‘ABC_3′}, {’employee’: ‘XYZ_6’, ‘company’: ‘ABC_3’}]

示例 2：假设我们有学生成绩和分数的字典列表。

students = [
    {'mark': '65','grade': 'C'},
    {'mark': '86','grade': 'A'},
    {'mark': '73','grade': 'B'},
    {'mark': '49','grade': 'D'},
    {'mark': '91','grade': 'A'},
    {'mark': '79','grade': 'B'}
]

现在我们需要通过“等级”键显示所有数据组。

代码：

Python3

# import required methods
from itertools import groupby
from operator import itemgetter
  
# dictionary
students = [
    {'mark': '65', 'grade': 'C'},
    {'mark': '86', 'grade': 'A'},
    {'mark': '73', 'grade': 'B'},
    {'mark': '49', 'grade': 'D'},
    {'mark': '91', 'grade': 'A'},
    {'mark': '79', 'grade': 'B'}
]
  
# Sort students data by grade key.
students = sorted(students, 
                  key = itemgetter('grade'))
  
# Display data grouped by grade
for key, value in groupby(students,
                          key = itemgetter('grade')):
    print(key)
    for k in value:
        print(k)

输出：

A
{'mark': '86', 'grade': 'A'}
{'mark': '91', 'grade': 'A'}
B
{'mark': '73', 'grade': 'B'}
{'mark': '79', 'grade': 'B'}
C
{'mark': '65', 'grade': 'C'}
D
{'mark': '49', 'grade': 'D'}