Re: [Configobj-develop] [python] problems with non standard types like, wx.Colour

[Michael F. <fuz...@vo...>]

Stef Mientki wrote:
> hello,
>
> I'm using ConfigObj for writing/reading inifiles for a couple of months.
> Until now I did a number of conversions myself,
> but now I discovered a number of switches,
> which in general do it much better than my own program (no wonder ;-)
> These are my switches
>
>     list_values = True,
>     write_empty_values = True,
>     unrepr = True )
>   
Looks good - except I can't remember how list values interact with 
unrepr (I don't use unrepr mode myself and I implemented for Turbogears 
- in fact Kevin Dangoor contributed the code I think). On the other hand 
if it is *working* for you then it must be fine...

> It looks really good, even for complex nested structures.
> But I've a few problems with non-standard types, like wx.Colour,
> which is basically a tupple with some constraints.
> In writing, ConfigObj writes: 
>
> CS_SN1 = [wx.Colour(224, 224, 224, 255),  True, True, True, False]
>
> that seems great, but ...
> ... I get an error if ConfigObj tries to read it back.
>
> So I made a workaround, which works ok:
>
>   def Write (self, name, value):
>     if type(value) in [bool,int,str,float,list,tuple] :
>       self[self.Section][name.strip()] = value
>     else :
>       try :
>         # try to convert to tupple,
>         # something like a wx.Colour can not be read back,
>         # but can just as well be written/read as a tupple
>         value = tuple ( value )
>         self[self.Section][name.strip()] = value
>       except :
>         self[self.Section][name.strip()] = str(value)
>     self.Modified = True
>
> Why can't ConfigObj not read back wx.Colour (and others) ?
> Any switches not set correct ?
> And if it's not possible, is my workaround correct (btw doesn't work for 
> nested non-standard types) ?
>   

ConfigObj is not *intended* to read in (or write out) non-standard types 
in unrepr mode. A way of extending unrepr mode for this would be nice (a 
way of recognising non standard types and reprs in the read/write 
phases), but as I don't use unrepr mode it would have to be implemented 
by someone else. It shouldn't actually be very hard - the difficult part 
is deciding on a clean and simple API (a dictionary of names mapping to 
types - although 'wx.Color' might be a problem because unrepr uses the 
Python parser and that is a dotted name rather than just a name).

Your fix - to write the value out as a tuple if it can be converted is 
clever, but in general it might not 'do the right thing' when read back 
in.  (For users who aren't aware of this behaviour.) In general I prefer 
to raise an exception than do clever tricks.

For handling custom types you can use 'validate.py' and configspecs, but 
off the top of my head I don't think that they work well with unrepr mode.

How about using the walk method to recursively change wx.Colour objects 
into tuples before writing?

Michael

> thanks,
> Stef Mientki
>
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