python二维数组创建赋值问题：更改单个值却更改了所有项的值

tianshuiyimo2023-12-13 12:18

python 复制代码

test_list = []
dic1 = {}
test_list = [dic1 for _ in range(3)]
ll = [1, 2, 3]

for i in range(3):
    test_list[i]['value'] = ll[i]

print(test_list)

运行结果：每次赋值都更改了所有项

原因：python的二位数据创建方式就是这样，官方文档中有描述What has happened is that $\[$ ] is a one-element list containing an empty list,

so all three elements of $\[$ ] * 3 are references to this single empty list.

Modifying any of the elements of lists modifies this single list. You can create a list of different lists this way:

python 复制代码

>>> lists = [[] for i in range(3)]
>>> lists[0].append(3)
>>> lists[1].append(5)
>>> lists[2].append(7)
>>> lists
[[3], [5], [7]]

那么，将上述代码修改为：

python 复制代码

test_list = []
test_list = [{} for _ in range(3)]
ll = [1, 2, 3]

for i in range(3):
    test_list[i]['value'] = ll[i]

print(test_list)

结果正确：