Make rel_dfs of from_dfs optional

changelog.md

@@ -9,6 +9,7 @@
 ## New features
 
 * Allow passing a `neo4j.Driver` instance as input to `from_neo4j`, in which case the driver will be used internally to fetch the graph data using a simple query
+* The `rel_dfs` parameter of `from_dfs` is now optional, allowing for loading a graph with only nodes and no relationships
 
 
 ## Bug fixes

python-wrapper/src/neo4j_viz/pandas.py

@@ -27,13 +27,19 @@ def _parse_validation_error(e: ValidationError, entity_type: type[BaseModel]) ->
 
 
 def _from_dfs(
-    node_dfs: Optional[DFS_TYPE],
-    rel_dfs: DFS_TYPE,
+    node_dfs: Optional[DFS_TYPE] = None,
+    rel_dfs: Optional[DFS_TYPE] = None,
     node_radius_min_max: Optional[tuple[float, float]] = (3, 60),
     rename_properties: Optional[dict[str, str]] = None,
     dropna: bool = False,
 ) -> VisualizationGraph:
-    relationships = _parse_relationships(rel_dfs, rename_properties=rename_properties, dropna=dropna)
+    if node_dfs is None and rel_dfs is None:
+        raise ValueError("At least one of `node_dfs` or `rel_dfs` must be provided")
+
+    if rel_dfs is None:
+        relationships = []
+    else:
+        relationships = _parse_relationships(rel_dfs, rename_properties=rename_properties, dropna=dropna)
 
     if node_dfs is None:
         has_size = False
@@ -124,8 +130,8 @@ def _parse_relationships(
 
 
 def from_dfs(
-    node_dfs: Optional[DFS_TYPE],
-    rel_dfs: DFS_TYPE,
+    node_dfs: Optional[DFS_TYPE] = None,
+    rel_dfs: Optional[DFS_TYPE] = None,
     node_radius_min_max: Optional[tuple[float, float]] = (3, 60),
 ) -> VisualizationGraph:
     """
@@ -137,11 +143,12 @@ def from_dfs(
 
     Parameters
     ----------
-    node_dfs: Optional[Union[DataFrame, Iterable[DataFrame]]]
+    node_dfs: Optional[Union[DataFrame, Iterable[DataFrame]]], optional
         DataFrame or iterable of DataFrames containing node data.
         If None, the nodes will be created from the source and target node ids in the rel_dfs.
-    rel_dfs: Union[DataFrame, Iterable[DataFrame]]
+    rel_dfs: Optional[Union[DataFrame, Iterable[DataFrame]]], optional
         DataFrame or iterable of DataFrames containing relationship data.
+        If None, no relationships will be created.
     node_radius_min_max : tuple[float, float], optional
         Minimum and maximum node radius.
         To avoid tiny or huge nodes in the visualization, the node sizes are scaled to fit in the given range.

python-wrapper/tests/test_pandas.py

@@ -190,3 +190,39 @@ def test_rel_errors() -> None:
         match=r"Error for relationship column 'caption_size' with provided input '-300.0'. Reason: Input should be greater than 0",
     ):
         from_dfs(nodes, relationships)
+
+
+def test_from_dfs_no_rels() -> None:
+    nodes = [
+        DataFrame(
+            {
+                "id": [0],
+                "caption": ["A"],
+                "size": [1337],
+                "color": "#FF0000",
+            }
+        ),
+        DataFrame(
+            {
+                "id": [1],
+                "caption": ["B"],
+                "size": [42],
+                "color": "#FF0000",
+            }
+        ),
+    ]
+    VG = from_dfs(nodes, [], node_radius_min_max=(42, 1337))
+
+    assert len(VG.nodes) == 2
+
+    assert VG.nodes[0].id == 0
+    assert VG.nodes[0].caption == "A"
+    assert VG.nodes[0].size == 1337
+    assert VG.nodes[0].color == Color("#ff0000")
+
+    assert VG.nodes[1].id == 1
+    assert VG.nodes[1].caption == "B"
+    assert VG.nodes[1].size == 42
+    assert VG.nodes[0].color == Color("#ff0000")
+
+    assert len(VG.relationships) == 0