app/django/core/serializers/pyyaml.py
author Todd Larsen <tlarsen@google.com>
Fri, 26 Sep 2008 19:47:07 +0000
changeset 204 7075c27170f2
parent 54 03e267d67478
child 323 ff1a9aa48cfd
permissions -rw-r--r--
Add ModelWithFieldAttributes *before* PolyModel, so that everything does not become a "ModelWithFieldAttributes" in the Datastore. The way PolyModel works, each Model class hierarchy is stored in the Datastore as the class that directly inherited from PolyModel. So, we do not want to insert ModelWithFieldAttributes *after* PolyModel by inheriting *from* PolyModel, or everything would just be a ModelWithFieldAttributes in the Datastore, instead of Person, Work, Group, etc.

"""
YAML serializer.

Requires PyYaml (http://pyyaml.org/), but that's checked for in __init__.
"""

from django.db import models
from django.core.serializers.python import Serializer as PythonSerializer
from django.core.serializers.python import Deserializer as PythonDeserializer
try:
    from cStringIO import StringIO
except ImportError:
    from StringIO import StringIO
import yaml

class Serializer(PythonSerializer):
    """
    Convert a queryset to YAML.
    """
    
    internal_use_only = False
    
    def handle_field(self, obj, field):
        # A nasty special case: base YAML doesn't support serialization of time
        # types (as opposed to dates or datetimes, which it does support). Since
        # we want to use the "safe" serializer for better interoperability, we
        # need to do something with those pesky times. Converting 'em to strings
        # isn't perfect, but it's better than a "!!python/time" type which would
        # halt deserialization under any other language.
        if isinstance(field, models.TimeField) and getattr(obj, field.name) is not None:
            self._current[field.name] = str(getattr(obj, field.name))
        else:
            super(Serializer, self).handle_field(obj, field)
    
    def end_serialization(self):
        self.options.pop('stream', None)
        self.options.pop('fields', None)
        yaml.safe_dump(self.objects, self.stream, **self.options)

    def getvalue(self):
        return self.stream.getvalue()

def Deserializer(stream_or_string, **options):
    """
    Deserialize a stream or string of YAML data.
    """
    if isinstance(stream_or_string, basestring):
        stream = StringIO(stream_or_string)
    else:
        stream = stream_or_string
    for obj in PythonDeserializer(yaml.load(stream)):
        yield obj