Add fetch_entity_names method (#230)

**Fetch entity names**: this is an implementation of a few DC website
features:
- The name endpoint of the internal API
- Fetch the english names from the `name` property.
- Fetch the i18n name using the `nameWithLanguage` property (the
website automatically resolves the user's locale, this method takes it
as an argument)

Author: jm-rivera

Diff for: datacommons_client/endpoints/node.py

@@ -6,11 +6,17 @@
 from datacommons_client.endpoints.payloads import NodeRequestPayload
 from datacommons_client.endpoints.payloads import normalize_properties_to_string
 from datacommons_client.endpoints.response import NodeResponse
+from datacommons_client.models.node import Name
 from datacommons_client.models.node import Node
 from datacommons_client.utils.graph import build_ancestry_map
 from datacommons_client.utils.graph import build_ancestry_tree
 from datacommons_client.utils.graph import fetch_parents_lru
 from datacommons_client.utils.graph import flatten_ancestry
+from datacommons_client.utils.names import DEFAULT_NAME_LANGUAGE
+from datacommons_client.utils.names import DEFAULT_NAME_PROPERTY
+from datacommons_client.utils.names import extract_name_from_english_name_property
+from datacommons_client.utils.names import extract_name_from_property_with_language
+from datacommons_client.utils.names import NAME_WITH_LANGUAGE_PROPERTY
 
 ANCESTRY_MAX_WORKERS = 10
 
@@ -194,6 +200,58 @@ def fetch_all_classes(
         next_token=next_token,
     )
 
+  def fetch_entity_names(
+      self,
+      entity_dcids: str | list[str],
+      language: Optional[str] = DEFAULT_NAME_LANGUAGE,
+      fallback_language: Optional[str] = None,
+  ) -> dict[str, Name]:
+    """
+        Fetches entity names in the specified language, with optional fallback to English.
+        Args:
+          entity_dcids: A single DCID or a list of DCIDs to fetch names for.
+          language: Language code (e.g., "en", "es"). Defaults to "en" (DEFAULT_NAME_LANGUAGE).
+          fallback_language: If provided, this language will be used as a fallback if the requested
+            language is not available. If not provided, no fallback will be used.
+        Returns:
+          A dictionary mapping each DCID to a dictionary with the mapped name, language, and
+            the property used.
+        """
+
+    # Check if entity_dcids is a single string. If so, convert it to a list.
+    if isinstance(entity_dcids, str):
+      entity_dcids = [entity_dcids]
+
+    # If langauge is English, use the more efficient 'name' property.
+    name_property = (DEFAULT_NAME_PROPERTY if language == DEFAULT_NAME_LANGUAGE
+                     else NAME_WITH_LANGUAGE_PROPERTY)
+
+    # Fetch names the given entity DCIDs.
+    data = self.fetch_property_values(
+        node_dcids=entity_dcids, properties=name_property).get_properties()
+
+    names: dict[str, Name] = {}
+
+    # Iterate through the fetched data and populate the names dictionary.
+    for dcid, properties in data.items():
+      if language == "en":
+        name = extract_name_from_english_name_property(properties=properties)
+        lang_used = "en"
+      else:
+        name, lang_used = extract_name_from_property_with_language(
+            properties=properties,
+            language=language,
+            fallback_language=fallback_language,
+        )
+      if name:
+        names[dcid] = Name(
+            value=name,
+            language=lang_used,
+            property=name_property,
+        )
+
+    return names
+
   def fetch_entity_parents(
       self,
       entity_dcids: str | list[str],

Diff for: datacommons_client/endpoints/response.py

@@ -2,6 +2,7 @@
 from dataclasses import field
 from typing import Any, Dict, List
 
+from datacommons_client.models.base import SerializableMixin
 from datacommons_client.models.node import Arcs
 from datacommons_client.models.node import NextToken
 from datacommons_client.models.node import NodeDCID
@@ -13,7 +14,6 @@
 from datacommons_client.models.resolve import Entity
 from datacommons_client.utils.data_processing import flatten_properties
 from datacommons_client.utils.data_processing import observations_as_records
-from datacommons_client.utils.data_processing import SerializableMixin
 
 
 @dataclass

Diff for: datacommons_client/models/base.py

@@ -0,0 +1,39 @@
+from dataclasses import asdict
+import json
+from typing import Any, Dict
+
+
+class SerializableMixin:
+  """Provides serialization methods for the Response dataclasses."""
+
+  def to_dict(self, exclude_none: bool = True) -> Dict[str, Any]:
+    """Converts the instance to a dictionary.
+
+        Args:
+            exclude_none: If True, only include non-empty values in the response.
+
+        Returns:
+            Dict[str, Any]: The dictionary representation of the instance.
+        """
+
+    def _remove_none(data: Any) -> Any:
+      """Recursively removes None or empty values from a dictionary or list."""
+      if isinstance(data, dict):
+        return {k: _remove_none(v) for k, v in data.items() if v is not None}
+      elif isinstance(data, list):
+        return [_remove_none(item) for item in data]
+      return data
+
+    result = asdict(self)
+    return _remove_none(result) if exclude_none else result
+
+  def to_json(self, exclude_none: bool = True) -> str:
+    """Converts the instance to a JSON string.
+
+        Args:
+            exclude_none: If True, only include non-empty values in the response.
+
+        Returns:
+            str: The JSON string representation of the instance.
+        """
+    return json.dumps(self.to_dict(exclude_none=exclude_none), indent=2)

Diff for: datacommons_client/models/node.py

@@ -2,7 +2,7 @@
 from dataclasses import field
 from typing import Any, Dict, List, Optional, TypeAlias
 
-from datacommons_client.utils.data_processing import SerializableMixin
+from datacommons_client.models.base import SerializableMixin
 
 NextToken: TypeAlias = Optional[str]
 NodeDCID: TypeAlias = str
@@ -40,6 +40,21 @@ def from_json(cls, json_data: Dict[str, Any]) -> "Node":
     )
 
 
+@dataclass
+class Name(SerializableMixin):
+  """Represents a name associated with an Entity (node).
+
+    Attributes:
+        value: The name of the Entity
+        language: The language of the name
+        property: The property used to get the name
+    """
+
+  value: str
+  language: str
+  property: str
+
+
 @dataclass
 class NodeGroup:
   """Represents a group of nodes in the Data Commons knowledge graph.

Diff for: datacommons_client/tests/endpoints/test_node_endpoint.py

@@ -4,7 +4,10 @@
 from datacommons_client.endpoints.base import API
 from datacommons_client.endpoints.node import NodeEndpoint
 from datacommons_client.endpoints.response import NodeResponse
+from datacommons_client.models.node import Name
 from datacommons_client.models.node import Node
+from datacommons_client.utils.names import DEFAULT_NAME_PROPERTY
+from datacommons_client.utils.names import NAME_WITH_LANGUAGE_PROPERTY
 
 
 def test_node_endpoint_initialization():
@@ -198,6 +201,132 @@ def test_node_endpoint_fetch_property_values_string_vs_list():
   )
 
 
+@patch(
+    "datacommons_client.endpoints.node.extract_name_from_english_name_property")
+def test_fetch_entity_names_english(mock_extract_name):
+  """Test fetching names in English (default behavior)."""
+  mock_extract_name.return_value = "Guatemala"
+  api_mock = MagicMock()
+  endpoint = NodeEndpoint(api=api_mock)
+
+  # Mock the response from fetch_property_values
+  endpoint.fetch_property_values = MagicMock(return_value=NodeResponse(
+      data={
+          "dc/123": {
+              "properties": {
+                  DEFAULT_NAME_PROPERTY: [{
+                      "value": "Guatemala"
+                  }]
+              }
+          }
+      }))
+
+  result = endpoint.fetch_entity_names("dc/123")
+  endpoint.fetch_property_values.assert_called_once_with(
+      node_dcids=["dc/123"], properties=DEFAULT_NAME_PROPERTY)
+  assert result == {
+      "dc/123":
+          Name(
+              value="Guatemala",
+              language="en",
+              property=DEFAULT_NAME_PROPERTY,
+          )
+  }
+
+  mock_extract_name.assert_called_once()
+
+
+@patch(
+    "datacommons_client.endpoints.node.extract_name_from_property_with_language"
+)
+def test_fetch_entity_names_non_english(mock_extract_name):
+  """Test fetching names in a non-English language."""
+  mock_extract_name.return_value = ("Californie", "fr")
+  api_mock = MagicMock()
+  endpoint = NodeEndpoint(api=api_mock)
+
+  endpoint.fetch_property_values = MagicMock(return_value=NodeResponse(
+      data={
+          "dc/123": {
+              "properties": {
+                  NAME_WITH_LANGUAGE_PROPERTY: [{
+                      "value": "Californie",
+                      "lang": "fr"
+                  }]
+              }
+          }
+      }))
+
+  result = endpoint.fetch_entity_names("dc/123", language="fr")
+  endpoint.fetch_property_values.assert_called_once_with(
+      node_dcids=["dc/123"], properties=NAME_WITH_LANGUAGE_PROPERTY)
+  assert result == {
+      "dc/123":
+          Name(
+              value="Californie",
+              language="fr",
+              property=NAME_WITH_LANGUAGE_PROPERTY,
+          )
+  }
+
+  mock_extract_name.assert_called_once()
+
+
+@patch(
+    "datacommons_client.endpoints.node.extract_name_from_property_with_language"
+)
+def test_fetch_entity_names_with_fallback(mock_extract_name_lang):
+  """Test fallback to another language when target language is unavailable."""
+  mock_extract_name_lang.return_value = ("Chiquimula", "en")
+  api_mock = MagicMock()
+  endpoint = NodeEndpoint(api=api_mock)
+
+  endpoint.fetch_property_values = MagicMock(return_value=NodeResponse(
+      data={
+          "dc/123": {
+              "properties": {
+                  NAME_WITH_LANGUAGE_PROPERTY: [{
+                      "value": "Chiquimula",
+                      "lang": "en"
+                  }]
+              }
+          }
+      }))
+
+  result = endpoint.fetch_entity_names("dc/123",
+                                       language="fr",
+                                       fallback_language="en")
+
+  assert result == {
+      "dc/123":
+          Name(
+              value="Chiquimula",
+              language="en",
+              property=NAME_WITH_LANGUAGE_PROPERTY,
+          )
+  }
+
+
+@patch(
+    "datacommons_client.endpoints.node.extract_name_from_property_with_language"
+)
+def test_fetch_entity_names_no_result(mock_extract_name_lang):
+  """Test case when no name is found."""
+  mock_extract_name_lang.return_value = (None, None)
+  api_mock = MagicMock()
+  endpoint = NodeEndpoint(api=api_mock)
+
+  endpoint.fetch_property_values = MagicMock(return_value=NodeResponse(
+      data={"dc/999": {
+          "properties": {}
+      }}))
+
+  result = endpoint.fetch_entity_names("dc/999",
+                                       language="es",
+                                       fallback_language="en")
+  assert result == {}
+
+
 @patch("datacommons_client.endpoints.node.fetch_parents_lru")
 def test_fetch_parents_cached_delegates_to_lru(mock_fetch_lru):
   mock_fetch_lru.return_value = (Node("B", "B name", "Region"),)

Diff for: datacommons_client/tests/test_names.py

@@ -0,0 +1,66 @@
+from datacommons_client.models.node import Node
+from datacommons_client.utils.names import extract_name_from_english_name_property
+from datacommons_client.utils.names import extract_name_from_property_with_language
+
+
+def test_extract_name_from_english_name_property_with_list():
+  """Test extracting name from a list of Nodes."""
+  properties = [Node(value="Test Name")]
+  result = extract_name_from_english_name_property(properties)
+  assert result == "Test Name"
+
+
+def test_extract_name_from_english_not_list():
+  """Test extracting name from a single Node (not in a list)."""
+  property_node = Node(value="Single Node Name")
+  result = extract_name_from_english_name_property(property_node)
+  assert result == "Single Node Name"
+
+
+def test_extract_name_from_property_with_language_match():
+  """Test extracting name when desired language is present."""
+  properties = [
+      Node(value="Nombre@es"),
+      Node(value="Name@en"),
+  ]
+  result = extract_name_from_property_with_language(properties,
+                                                    language="es",
+                                                    fallback_language="en")
+  assert result[0] == "Nombre"
+  assert result[1] == "es"
+
+
+def test_extract_name_from_property_with_language_fallback():
+  """Test fallback to English when desired language is not found."""
+  properties = [
+      Node(value="Name@en"),
+      Node(value="Nom@fr"),
+      Node(value="Nome@it"),
+  ]
+  result = extract_name_from_property_with_language(properties,
+                                                    language="de",
+                                                    fallback_language="it")
+  assert result[0] == "Nome"
+  assert result[1] == "it"
+
+
+def test_extract_name_from_property_with_language_no_fallback():
+  """Test no result when language is not found and fallback is disabled."""
+  properties = [
+      Node(value="Name@en"),
+      Node(value="Nom@fr"),
+  ]
+  result = extract_name_from_property_with_language(properties, language="de")
+  assert result[0] is None
+  assert result[1] is None
+
+
+def test_extract_name_from_property_without_language_tags():
+  """Test that properties without language tags are skipped."""
+  properties = [
+      Node(value="Plain str"),
+      Node(value="Name@en"),
+  ]
+  result = extract_name_from_property_with_language(properties, language="en")
+  assert result[0] == "Name"
+  assert result[1] == "en"