如何从Python中读取Perl数据结构？ [英] How can I read Perl data structures from Python?

问题描述

我经常看到人们使用Perl数据结构来代替配置文件;即包含以下内容的单独文件：

I've often seen people use Perl data structures in lieu of configuration files; i.e. a lone file containing only:

%config = (
    'color' => 'red',
    'numbers' => [5, 8],
    qr/^spam/ => 'eggs'
);

使用纯Python将这些文件的内容转换为Python等效的数据结构？暂时我们可以假设没有真正的表达式来评估，只有结构化数据。

What's the best way to convert the contents of these files into Python-equivalent data structures, using pure Python? For the time being we can assume that there are no real expressions to evaluate, only structured data.

推荐答案

情况是。这里是我的假设：你将做一次从Perl到Python的转换。

Not sure what the use case is. Here's my assumption: you're going to do a one-time conversion from Perl to Python.

Perl有这个

%config = (
    'color' => 'red',
    'numbers' => [5, 8],
    qr/^spam/ => 'eggs'
);

在Python中，它将是

In Python, it would be

config = {
    'color' : 'red',
    'numbers' : [5, 8],
    re.compile( "^spam" ) : 'eggs'
}

所以，我猜这是一堆RE替换

So, I'm guessing it's a bunch of RE's to replace

• ％variable =（ with variable = {


• ）; 与} / li>

• variable => value with variable：value


• qr /.../ = ; 与 re.compile（r...）：value

• %variable = ( with variable = {
• ); with }
• variable => value with variable : value
• qr/.../ => with re.compile( r"..." ) : value

但是，Python的内置 dict 不会使用regex作为散列键做任何异常。为此，您必须编写自己的 dict 子类，并覆盖 __ getitem __ 以单独检查REGEX键。

However, Python's built-in dict doesn't do anything unusual with a regex as a hash key. For that, you'd have to write your own subclass of dict, and override __getitem__ to check REGEX keys separately.

class PerlLikeDict( dict ):
    pattern_type= type(re.compile(""))
    def __getitem__( self, key ):
        if key in self:
            return super( PerlLikeDict, self ).__getitem__( key )
        for k in self:
            if type(k) == self.pattern_type:
                if k.match(key):
                    return self[k]
        raise KeyError( "key %r not found" % ( key, ) )

这里是使用类似Perl的dict的例子。

Here's the example of using a Perl-like dict.

>>> pat= re.compile( "hi" )
>>> a = { pat : 'eggs' } # native dict, no features.
>>> x=PerlLikeDict( a )
>>> x['b']= 'c'
>>> x
{<_sre.SRE_Pattern object at 0x75250>: 'eggs', 'b': 'c'}
>>> x['b']
'c'
>>> x['ji']
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 10, in __getitem__
KeyError: "key 'ji' not found"
>>> x['hi']
'eggs'

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