Add new serializer: better YAML

apps/common/serializers/better_yaml.py

@@ -0,0 +1,103 @@
+# better_yaml.py
+
+"""
+Customized YAML serializer, with more condensed and readable output.
+Rather than producing a flat list of objects with the same three attributes:
+
+    - fields: {...}
+      model: modelname
+      pk: 123
+
+This serializer nests the data, grouping by model name, then indexing by
+primary key. For example, instead of this output, as produced by the default
+YAML serializer:
+
+    - fields: {name: blue}
+      model: app.firstmodel
+      pk: 3
+    - fields: {name: red}
+      model: app.firstmodel
+      pk: 1
+    - fields: {name: green}
+      model: app.firstmodel
+      pk: 2
+    - fields: {name: crumbly}
+      model: app.secondmodel
+      pk: 2
+    - fields: {name: squishy}
+      model: app.secondmodel
+      pk: 1
+
+You'll get this output:
+
+    app.firstmodel:
+      1: {name: red}
+      2: {name: green}
+      3: {name: blue}
+    app.secondmodel:
+      1: {name: squishy}
+      2: {name: crumbly}
+
+To use this customized serializer and deserializer, save this file
+somewhere in your Django project, then add this to your settings.py:
+
+    SERIALIZATION_MODULES = {
+        'yaml': 'path.to.better_yaml',
+    }
+
+Note that this serializer is NOT compatible with the default Django
+YAML serializer; this one uses nested dictionaries, while the default
+one uses a flat list of object dicts.
+
+Requires PyYaml (http://pyyaml.org/), of course.
+"""
+
+from StringIO import StringIO
+import yaml
+
+from django.core.serializers.pyyaml import Serializer as YamlSerializer
+from django.core.serializers.python import Deserializer as PythonDeserializer
+from django.utils.encoding import smart_unicode
+
+class Serializer (YamlSerializer):
+    """
+    Serialize database objects as nested dicts, indexed first by
+    model name, then by primary key.
+    """
+    def start_serialization(self):
+        self._current = None
+        self.objects = {}
+
+    def end_object(self, obj):
+        model = smart_unicode(obj._meta)
+        pk = obj._get_pk_val()
+
+        if model not in self.objects:
+            self.objects[model] = {}
+
+        self.objects[model][pk] = self._current
+        self._current = None
+
+
+def Deserializer(stream_or_string, **options):
+    """
+    Deserialize a stream or string of YAML data,
+    as written by the Serializer above.
+    """
+    if isinstance(stream_or_string, basestring):
+        stream = StringIO(stream_or_string)
+    else:
+        stream = stream_or_string
+
+    # Reconstruct the flat object list as PythonDeserializer expects
+    # NOTE: This could choke on large data sets, since it
+    # constructs the flattened data list in memory
+    data = []
+    for model, objects in yaml.load(stream).iteritems():
+        # Add the model name back into each object dict
+        for pk, fields in objects.iteritems():
+            data.append({'model': model, 'pk': pk, 'fields': fields})
+
+    # Deserialize the flattened data
+    for obj in PythonDeserializer(data, **options):
+        yield obj

settings.py

@@ -233,6 +233,10 @@ PAGINATION_INVALID_PAGE_RAISES_404 = True
 #---------- Search ------------------
 SEARCH_SHOW_OBJECT_TYPE = False
 
+SERIALIZATION_MODULES = {
+    'better_yaml': 'common.serializers.better_yaml',
+}
+
 try:
     from settings_local import *
 except ImportError: