[Python-Dev] New miniconf module

[Michael Foord]

Armin Rigo wrote:
> Hi,
>
> On Thu, Jul 27, 2006 at 03:39:39AM -0400, Sylvain Fourmanoit wrote:
>   
>> Having JSON there would indeed be nice: In fact, I recall being initially 
>> surprised it was not supported by the standard library.
>>
>> But is there a need to choose? Why not have both? The miniconf approach 
>> has its advantages and differences:
>>     
>
> I support this point of view: miniconf fills the hole that the stdlib
> leaves for a safe and cross-version dumper/loader for simple objects
> using the Python syntax.  In the same spirit, maybe it could be slightly
> re-oriented towards a dumper/loader for more than config files; for
> example, it could provide a safe inverse of repr() for common built-in
> types.  Such a functionality has been discussed here a few times if I
> remember correctly, but the code in miniconf is very close to providing
> it.
>   
ConfigObj [1] gained an 'unrepr' mode a while back. The code is simple, 
and originally came from CherryPy.

It can (safely) unrepr basic datatypes.

import compiler

def getObj(s):
    s = "a=" + s
    p = compiler.parse(s)
    return p.getChildren()[1].getChildren()[0].getChildren()[1]

class UnknownType(Exception):
    pass

class Builder:
   
    def build(self, o):
        m = getattr(self, 'build_' + o.__class__.__name__, None)
        if m is None:
            raise UnknownType(o.__class__.__name__)
        return m(o)
   
    def build_List(self, o):
        return map(self.build, o.getChildren())
   
    def build_Const(self, o):
        return o.value
   
    def build_Dict(self, o):
        d = {}
        i = iter(map(self.build, o.getChildren()))
        for el in i:
            d[el] = i.next()
        return d
   
    def build_Tuple(self, o):
        return tuple(self.build_List(o))
   
    def build_Name(self, o):
        if o.name == 'None':
            return None
        if o.name == 'True':
            return True
        if o.name == 'False':
            return False
       
        # An undefinted Name
        raise UnknownType('Undefined Name')
   
    def build_Add(self, o):
        real, imag = map(self.build_Const, o.getChildren())
        try:
            real = float(real)
        except TypeError:
            raise UnknownType('Add')
        if not isinstance(imag, complex) or imag.real != 0.0:
            raise UnknownType('Add')
        return real+imag
   
    def build_Getattr(self, o):
        parent = self.build(o.expr)
        return getattr(parent, o.attrname)
   
    def build_UnarySub(self, o):
        return -self.build_Const(o.getChildren()[0])
   
    def build_UnaryAdd(self, o):
        return self.build_Const(o.getChildren()[0])

def unrepr(s):
    if not s:
        return s
    return Builder().build(getObj(s))


HTH

Michael Foord

[1] http://www.voidspace.org.uk/python/configobj.html


>
> A bientot,
>
> Armin
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