将列表列表转换为字典 [重复]答案

【问题标题】：Convert a list of lists to dictionary [duplicate]将列表列表转换为字典 [重复]
【发布时间】：2019-11-27 06:46:08
【问题描述】：

我有一个包含六个列表的列表

lst = [
    ['2.2.5', '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All'],
    ['2.2.6', '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All'],
    ['2.2.5', '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App'],
    ['2.2.6', '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App'],
    ['2.2.5', '/usr/local/share/dotnet/shared/Microsoft.NETCore.App'],
    ['2.2.6', '/usr/local/share/dotnet/shared/Microsoft.NETCore.App']
]

我正在尝试将其转换为

{
    "2.2.5": ['/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All/2.2.5',
              '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App/2.2.5',
              '/usr/local/share/dotnet/shared/Microsoft.NETCore.App/2.2.5'],
    "2.2.6": ['/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All/2.2.6',
              '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App/2.2.6',
              '/usr/local/share/dotnet/shared/Microsoft.NETCore.App/2.2.6']
}

到目前为止，这是我所做的：

to_dict = {key[0]: [value[1] + '/' + value[0] for value in lst] for key in lst}

这会返回

{'2.2.5': ['/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All/2.2.5',
           '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All/2.2.6',
           '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App/2.2.5',
           '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App/2.2.6',
           '/usr/local/share/dotnet/shared/Microsoft.NETCore.App/2.2.5',
           '/usr/local/share/dotnet/shared/Microsoft.NETCore.App/2.2.6'],
 '2.2.6': ['/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All/2.2.5',
           '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All/2.2.6',
           '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App/2.2.5',
           '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App/2.2.6',
           '/usr/local/share/dotnet/shared/Microsoft.NETCore.App/2.2.5',
           '/usr/local/share/dotnet/shared/Microsoft.NETCore.App/2.2.6']}

内部循环从索引1 到lst 添加所有内容。我应该如何添加适合其键的值？

【问题讨论】：

啊！在 Google 中搜索时应该使用元组
dct = dict((a[0], [b[1]+'/'+a[0] for b in lst if b[0] == a[0]]) for a in lst)
@AniketSahrawat 你能添加这个作为答案吗？这是一个很好的实现

标签： python

【解决方案1】：

你可以这样做。

lst = [
['2.2.5', '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All'],
['2.2.6', '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All'],
['2.2.5', '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App'],
['2.2.6', '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App'],
['2.2.5', '/usr/local/share/dotnet/shared/Microsoft.NETCore.App'],
['2.2.6', '/usr/local/share/dotnet/shared/Microsoft.NETCore.App']
]
from collections import defaultdict
c=defaultdict(list)
[c[i].append(j) for i,j in lst]
print c

输出： defaultdict(<type 'list'>, {'2.2.5': ['/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All', '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App', '/usr/local/share/dotnet/shared/Microsoft.NETCore.App'], '2.2.6': ['/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All', '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App', '/usr/local/share/dotnet/shared/Microsoft.NETCore.App']})

【讨论】：

【解决方案2】：

使用defaultdict 或dict.setdefault() 方法：

lst = [
    ['2.2.5', '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All'],
    ['2.2.6', '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All'],
    ['2.2.5', '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App'],
    ['2.2.6', '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App'],
    ['2.2.5', '/usr/local/share/dotnet/shared/Microsoft.NETCore.App'],
    ['2.2.6', '/usr/local/share/dotnet/shared/Microsoft.NETCore.App']
]

out = {}
for k, v in lst:
    out.setdefault(k, []).append(v + '/' + k)

from pprint import pprint
pprint(out, width=30)

打印：

{'2.2.5': ['/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All/2.2.5',
           '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App/2.2.5',
           '/usr/local/share/dotnet/shared/Microsoft.NETCore.App/2.2.5'],
 '2.2.6': ['/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All/2.2.6',
           '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App/2.2.6',
           '/usr/local/share/dotnet/shared/Microsoft.NETCore.App/2.2.6']}

【讨论】：

【解决方案3】：

您可以将列表元素作为键值进行迭代（python 进行解包），并使用 dict.setdefault 将值列表设置为空并附加到列表中：

In [77]: out = {}                                                                                                                                                                                           

In [78]: for k, v in lst: 
    ...:     out.setdefault(k, []).append(v) 
    ...:                                                                                                                                                                                                    

In [79]: out                                                                                                                                                                                                
Out[79]: 
{'2.2.5': ['/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All',
  '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App',
  '/usr/local/share/dotnet/shared/Microsoft.NETCore.App'],
 '2.2.6': ['/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All',
  '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App',
  '/usr/local/share/dotnet/shared/Microsoft.NETCore.App']}

或 collections.defaultdict 与 list 工厂：

In [80]: out = collections.defaultdict(list)                                                                                                                                                                

In [81]: for k, v in lst: 
    ...:     out[k].append(v) 
    ...:      
    ...:                                                                                                                                                                                                    

In [82]: out                                                                                                                                                                                                
Out[82]: 
defaultdict(list,
            {'2.2.5': ['/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All',
              '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App',
              '/usr/local/share/dotnet/shared/Microsoft.NETCore.App'],
             '2.2.6': ['/usr/local/share/dotnet/shared/Microsoft.AspNetCore.All',
              '/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App',
              '/usr/local/share/dotnet/shared/Microsoft.NETCore.App']})

要将键字符串附加到值，请使用 f-strings 或 str.format（在不支持 f-strings 的版本上）：

对于dict.setdefault：

out.setdefault(k, []).append(f'{v}/{k}')
out.setdefault(k, []).append('{v}/{k}'.format(v=v, k=k))

对于collections.defaultdict：

out[k].append(f'{v}/{k}')
out[k].append('{v}/{k}'.format(v=v, k=k))

【讨论】：

这两种方法之间是否有任何性能？
@Akshay 都是用 C 实现的，但是后者导入了一个模块。