如何在Python中作为嵌套词典在Perl中实现多键哈希

Question

我有一些基本代码可以处理perl hash，我可以在其中解决：$ data {$ data {" wv2"} {789} {789} {pp1} {pp1}（或在中使用该实际文本作业）...但是我想使用Python词典做类似的事情。

Perl和Python中的几个简单程序，这些程序说明了我一直在尝试复制的内容，请如下： -

所以，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]

...和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]

从每个程序中输出以下： -

# 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'
                   }
        };

...和来自Python： -

# 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:Projects0-DevelopmentLXQueryCDB-Reviewdict.py", line 30, in <module>
    xdata["MC1"][123]["PP"] = "-15,-15C"  # ERROR: Key error 123
KeyError: 123

我已经尝试查找有关嵌套词典的信息...但是我所看的所有内容都没有清楚地解释该概念应该如何工作（无论如何，无论如何）....尤其是当使用的字典有"更深的"级别。

我一直在写perl代码已有25年了，但是才从Python开始。

运行Activestate Perl v5.16.3，构建1603和Anaconda Python 3.6.5 Windows 10 x64。

非常感谢任何想法或建议。

Answer 1

python不会像Perl对其哈希相同的方式自动化多级词典。在第二个和更深层次的级别上，您必须在向其添加更多键之前，将空的dict分配给更高级别的dict s：

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"

Answer 2

围绕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

...但这仍然意味着我必须"手动"定义一个dict时，每当我"发现'新的'value'... blah

）

尽管有固有的 gotcha！的误导性和（可能的）损坏dict内容，但实施嵌套词典的最佳方法是什么？似乎是解决问题的好方法...尤其是当值（无论如何在我当前的应用程序中）"永远不要看到一天的光"（它们是机器生成和验证的，然后才能进入我的应用程序）...因此，某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

感谢堆的建议和指针。