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

[Stef M. <s.m...@ru...>]

hello Michael,

Michael Foord wrote:
> 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...
>   
For what I've tested (just trial and error), unrepr, can handle a lot 
more complex structures:
e.g. with "unrepr=False", writing
  [[1, 2, 3, 4, 5], (1, 2), [1, (2, 3), [6]]]
result is reading:
   ['[1, 2, 3, 4, 5]', '(1, 2)', '[1, (2, 3), [6]]']
while "unrepr=True", it reads back exactly how it was written.

>   
>> 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.
>
>   
Ok, that's all too complex for me (at least for now).
As I want to store fairly complex structures, with a lot of special classes,
I'm also not sure if this really solves everything.
> How about using the walk method to recursively change wx.Colour objects 
> into tuples before writing?
>   
never heard of walk, again too complex for now ;-)

So thanks again,
I'm glad to know that the work around I use is not completely nonsense !

cheers,
Stef Mientki