Question

我有一个词典列表：

dicty = [defaultdict(list)] * (2)
dicty

[defaultdict(list, {}), defaultdict(list, {})]

现在我想知道如何索引这些词典？

我试过了：

dicty[0][0].append('abc')
dicty

[defaultdict(list, {0: ['abc']}), defaultdict(list, {0: ['abc']})]

但是你可以看到它附加在两个词典中。我想学习如何附加到单个字典中。

Answer 1

您可以使用：

dicty = [defaultdict(list) for _ in range(2)]

使用[defaultdict(list)] * (2)时，所有的词汇都指向内存中的同一个对象。

Answer 2

from collections import defaultdict

""" Here, you are saying that you wish to add twice "defaultdict(list)".
    These are the same objects. You are just duplicating the same one with *
"""
dicty = [defaultdict(list)] * (2)
dicty[0][0].append('abc')
print dicty
print dicty[0] is dicty[1], '\n'

""" However, here : you are creating two distinct dictionnaries.
"""
dicty = []
for _ in range(2):
    dicty.append(defaultdict(list))
dicty[0][0].append('abc')
print dicty
print dicty[0] is dicty[1]

# outputs :
#[defaultdict(<type 'list'>, {0: ['abc']}), defaultdict(<type 'list'>, {0: ['abc']})]
#True 

#[defaultdict(<type 'list'>, {0: ['abc']}), defaultdict(<type 'list'>, {})]
#False

列表中的索引词典

2 个答案: