尝试在python中创建字典列表时出现意外列表 [英] Unexpected list when trying to create a list of dictionaries in python

问题描述

我正在尝试创建字典列表.预期的结果是，对于5个学生，它在列表中应该有5个字典项，键是名称"和标记"(在列表中).我得到的输出是为迭代中的最后一个学生重复5次信息.请让我知道我在哪里出错.

I am trying to create a list of dictionary. The expected output is that for 5 Students, it should have 5 dictionary items in the list with keys being Name and Marks (in a list). The output that I get is having the information repeated 5 times for the last student in iteration. Please let me know where am I making an error.

import random
name_list=[]
name_list = ['A','B','C','D','E']
stud_dict=dict()
stud_dict_list = []
for name in name_list:
    mark_list = []
    for i in range(1,11):
        mark_list.append(random.randint(0,100))
    stud_dict['Name']=name
    stud_dict['Marks']=mark_list
    stud_dict_list.append(stud_dict)
print(stud_dict_list) 

output:
[{'Name': 'E', 'Marks': [91, 71, 93, 33, 52, 90, 97, 98, 41, 18]}, {'Name': 'E', 'Marks': [91, 71, 93, 33, 52, 90, 97, 98, 41, 18]}, {'Name': 'E', 'Marks': [91, 71, 93, 33, 52, 90, 97, 98, 41, 18]}, {'Name': 'E', 'Marks': [91, 71, 93, 33, 52, 90, 97, 98, 41, 18]}, {'Name': 'E', 'Marks': [91, 71, 93, 33, 52, 90, 97, 98, 41, 18]}]

推荐答案

已经问过很多遍了，但是我没有时间搜索确切的dup ATM，所以:

This has been asked many times but I don't have time to search for an exact dup ATM, so:

Python 从不复制内容.在这里，您将相同字典一遍又一遍地添加到列表中:

Python never copies things unless explicitely asked for. Here, you're adding the same dict to your list over and over again:

>>> import random
>>> name_list=[]
>>> name_list = ['A','B','C','D','E']
>>> stud_dict=dict()
>>> stud_dict_list = []
>>> for name in name_list:
...     mark_list = []
...     for i in range(1,11):
...         mark_list.append(random.randint(0,100))
...     stud_dict['Name']=name
...     stud_dict['Marks']=mark_list
...     stud_dict_list.append(stud_dict)
... 
>>> stud_dict
{'Name': 'E', 'Marks': [94, 51, 79, 82, 84, 76, 92, 96, 7, 52]}
>>> id(stud_dict)
139663685096344
>>> [id(item) for item in stud_dict_list]
[139663685096344, 139663685096344, 139663685096344, 139663685096344, 139663685096344]
>>> 

由于它是完全相同的字典，因此该字典的每次更新当然都会反映在列表中.解决方案非常简单，每次都创建一个新字典:

Since it's the very same dict, each update of the dict will of course be reflected in the list. And the solution is quite simply to create a new dict each time:

import random
name_list = ['A','B','C','D','E']
stud_dict_list = []
for name in name_list:
    mark_list = []
    for i in range(1,11):
        mark_list.append(random.randint(0,100))
    stud_dict = {'Name': name, 'Marks': mark_list}
    stud_dict_list.append(stud_dict)

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