如何在Perl中将多键哈希实现为Python中的嵌套字典？

我有一些基本的代码来处理Perl哈希，在这里我可以处理如下元素：$data{“WV2”}{789}{PP1}（或者在赋值中使用该实际文本）……但是我想使用Python字典做类似的事情

下面是几个用Perl和Python编写的简单程序，它们演示了我一直试图复制的内容：-

因此，Perl代码：-

# hash.pl

use strict;
use warnings;

use Data::Dumper;

my %data = ();

my @reg_list = ( "MC1", "CA2", "WV2" );
my @site_list = ( 123, 456, 391, 287 );

$data{MC1}{4564}{PP}{1} = "-15,-15C";
$data{MC1}{4564}{PP}{2} = "5,5C";
$data{MC1}{4564}{PP}{3} = "-19,-19C";
$data{MC1}{4564}{PP}{4} = "-12,-12C";

printf("---- One:\n");
print Dumper(%data);                 # Ok, shows the full strucure

printf("---- Two:\n");
print Dumper($data{"MC2"});          # Shows as undef (sensible)

printf("---- Three:\n");
print Dumper($data{"MC1"});          # Ok, showing the key:values for each "site" key

printf("---- Four:\n");
print Dumper($data{"MC1"}{"4564"});  # Ok, shows the actual equality value above


# ---- This works Ok

my %xdata = ();
$xdata{"MC1"}{123}{"PP"} = "-15,-15C";
$xdata{"MC1"}{456}{"PP"} = "5,5C";
$xdata{"MC1"}{391}{"PP"} = "-19,-19C";
$xdata{"MC1"}{287}{"PP"} = "-12,-12C";

printf("---- One:\n");
print Dumper(%xdata);                # Ok, shows the full strucure


#pprint.pprint(data["MC2"]) 
#pprint.pprint(data["MC1"}{391]) 


# [eof]

…以及Python代码：-

# dict.py

import pprint
import collections

reg_list  = [ "MC1", "CA2", "WV2" ]
site_list = [ 123, 456, 391, 287 ]

#data = {}
data = collections.defaultdict(dict) # {}
data["MC1"][123] = "-15,-15C"
data["MC1"][456] = "5,5C"
data["MC1"][391] = "-19,-19C"
data["MC1"][287] = "-12,-12C"

print("---- One:")
pprint.pprint(data)              # Ok, shows the full strucure

print("---- Two:")
pprint.pprint(data["MC2"])       # Shows: {} [...Ok, undefined...]

print("---- Three:")
pprint.pprint(data["MC1"])       # Ok, showing the key:values for each "site" key

print("---- Four:")
pprint.pprint(data["MC1"][391])  # Ok, shows the actual equality value above

# ---- Cannot get the following to work

xdata = collections.defaultdict(dict) # {}
xdata["MC1"][123]["PP"] = "-15,-15C"  # ERROR: Key error 123
xdata["MC1"][456]["PP"] = "5,5C"
xdata["MC1"][391]["PP"] = "-19,-19C"
xdata["MC1"][287]["PP"] = "-12,-12C"

#pprint.pprint(data["MC2"]) 
#pprint.pprint(data["MC1"][391]) 

# [eof]

每个程序的输出如下所示：-

# Perl Output:

---- One:
$VAR1 = 'MC1';
$VAR2 = {
          '4564' => {
                      'PP' => {
                                '4' => '-12,-12C',
                                '1' => '-15,-15C',
                                '3' => '-19,-19C',
                                '2' => '5,5C'
                              }
                    }
        };
---- Two:
$VAR1 = undef;
---- Three:
$VAR1 = {
          '4564' => {
                      'PP' => {
                                '4' => '-12,-12C',
                                '1' => '-15,-15C',
                                '3' => '-19,-19C',
                                '2' => '5,5C'
                              }
                    }
        };
---- Four:
$VAR1 = {
          'PP' => {
                    '4' => '-12,-12C',
                    '1' => '-15,-15C',
                    '3' => '-19,-19C',
                    '2' => '5,5C'
                  }
        };
---- One:
$VAR1 = 'MC1';
$VAR2 = {
          '391' => {
                     'PP' => '-19,-19C'
                   },
          '456' => {
                     'PP' => '5,5C'
                   },
          '123' => {
                     'PP' => '-15,-15C'
                   },
          '287' => {
                     'PP' => '-12,-12C'
                   }
        };

…从Python中：-

# Python Output:-

---- One:
defaultdict(<class 'dict'>,
            {'MC1': {123: '-15,-15C',
                     287: '-12,-12C',
                     391: '-19,-19C',
                     456: '5,5C'}})
---- Two:
{}
---- Three:
{123: '-15,-15C', 287: '-12,-12C', 391: '-19,-19C', 456: '5,5C'}
---- Four:
'-19,-19C'
Traceback (most recent call last):
  File "C:\Projects\00-Development\LXQuery\CDB-Review\dict.py", line 30, in <module>
    xdata["MC1"][123]["PP"] = "-15,-15C"  # ERROR: Key error 123
KeyError: 123

#Python输出：-
----一:
defaultdict（，
{'MC1'：{123:'-15，-15C'，
287:“-12，-12C”，
391:“-19，-19C”，
456:'5,5C'}}）
----二:
{}
----三:
{123:'-15，-15C'，287:'-12，-12C'，391:'-19，-19C'，456:'5,5C'}
----四:
“-19，-19C”
回溯（最近一次呼叫最后一次）：
文件“C:\Projects\00 Development\LXQuery\CDB Review\dict.py”，第30行，在
扩展数据[“MC1”][123][“PP”]=“-15，-15C”#错误：键错误123
关键字错误：123

我试图查找有关嵌套字典的信息。。。但我所看到的一切并没有清楚地解释这个概念是如何运作的（无论如何，在我看来）。。。。尤其是在使用的词典有“更深层次”的时候

我写Perl代码已经25年了，但我只是从Python开始

在Windows 10 x64下运行ActiveState Perl v5.16.3、Build 1603和Anaconda Python 3.6.5

---

非常感谢您的任何想法或建议。

Python没有像Perl处理哈希那样自动激活多级字典。在第二级和更深一级，您必须将空的

dict

分配给更高级别的

dict

s，然后才能向其添加更多键：

xdata = collections.defaultdict(dict)
xdata["MC1"] = collections.defaultdict(dict)
xdata["MC1"][123]["PP"] = "-15,-15C"  # ERROR: Key error 123
xdata["MC1"][456]["PP"] = "5,5C"
xdata["MC1"][391]["PP"] = "-19,-19C"
xdata["MC1"][287]["PP"] = "-12,-12C"

---

解决问题的简单方法似乎是：-

xdata = collections.defaultdict(dict) # {}
xdata["MC1"][123] = {}                # Define the dict before using it
xdata["MC1"][123]["PP"] = "-15,-15C"  # Works Ok

…但这仍然意味着，每当我“发现”一个新的“值”时，我必须“手动”定义一个dict。。。废话

尽管与生俱来的抓到你了由于打字错误和（可能）听写内容损坏，似乎是解决这个问题的一个好办法。。。尤其是这些值（无论如何，在我当前的应用程序中）“永远看不到曙光”（它们是在进入我的应用程序之前由机器生成和验证的）。。。因此，一些可能有效的代码可能是：-

class Vividict(dict):
    def __missing__(self, key):
        value = self[key] = type(self)() # retain local pointer to value
        return value                     # faster to return than 
                                         # ...'dict lookup'

ydata = Vividict()

ydata["MC1"][123]["PP"] = "-15,-15C"
ydata["MC1"][456]["PP"] = "5,5C"
ydata["MC1"][391]["PP"] = "-19,-19C"
ydata["MC1"][287]["PP"] = "-12,-12C"

pprint.pprint(ydata)              # Ok, shows the full strucure

---

感谢堆中的建议和指针。

问题在于，当找不到密钥时，您正在初始化

defaultdict

以返回（正常）

dict

实例，这就是第二维度失败的原因。不标记为重复，因为这不是完全相同的问题，但请查看感谢指针，Selcuk。。我只使用defaultdict，因为我认为它将消除对整个结构进行初始化的需要（正如@mob在我的想法中指出的那样）。。。但看起来我仍然需要这样做，所以defaultdict可能不是最好的选择。显然，还有更多的研究要做。。。