Re: PyYAML and creating python objects from YAML code with YAMLObject ...

Hi Markus,


On 02/03/2011 12:04 PM, Markus Hubig wrote:
> Hi @all,
>
> ich have a yaml file containing several documents, like this:
>
> --- !Table
> Table:         {Name: SYSTEM_PARAMETER_TABLE, Get: 10, Set: 11}
> ConfigID:      {'No': 0xfb, Type: 0x02, Status: OR, Length: 2}
> SerialNum:     {'No': 0x01, Type: 0x04, Status: WR, Length: 4}
> HWVersion:     {'No': 0x02, Type: 0x06, Status: OR, Length: 4}
> FWVersion:     {'No': 0x03, Type: 0x06, Status: OR, Length: 4}
> Baudrate:      {'No': 0x04, Type: 0x02, Status: WR, Length: 2}
> ModuleName:    {'No': 0x05, Type: 0x80, Status: OR, Length: 16}
> ModuleCode:    {'No': 0x06, Type: 0x02, Status: OR, Length: 2}
> ModuleInfo1:   {'No': 0x07, Type: 0x00, Status: WR, Length: 1}
> ModuleInfo2:   {'No': 0x08, Type: 0x00, Status: WR, Length: 1}

[...]

> and I wanna use this 'tables' to construct nested python classes by
> subclassing 'YAMLObject'.
> My first attempt was like this:
>
> class Row(object):
>      def __init__(self, *args, **kwargs):
>          self.__dict__.update(kwargs)
>      def __repr__(self):
>          return "%s" % self.__class__.__name__
> class Table(YAMLObject):
> """Spezialized Class for wraping YAML Data structures to python objects"""
>      yaml_tag = u'!Table'
>      def __init__(self, *args, **kwargs):
[...]

PyYAML follows pickle protocol when serializing and deserializing 
YAMLObject instances, which means it never calls the object constructor. 
  However you can define __getstate__ and/or __setstate__ methods. 
`__getstate__()` takes no arguments and returns a dictionary of object 
attributes, `__setstate__()` takes one argument, the said dictionary, 
and initializes the object.

See,
http://docs.python.org/library/pickle.html#object.__getstate__

Hope it helps, let me know if it's still not clear to you.

Kirill

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