implement __repr__ for PowerGridModel

src/power_grid_model/_core/power_grid_model.py

@@ -120,6 +120,26 @@ def __deepcopy__(self, memo: dict[int, Any]) -> "PowerGridModel":
 
         return new_model
 
+    def __repr__(self) -> str:
+        """Return a string representation of the current model.
+
+        This includes the total number of components and the number of components per component type of the model.
+
+        Returns:
+            String representation of the model
+        """
+        try:
+            component_count = self.all_component_count
+        except TypeError:
+            component_count = {}
+
+        message = f"{self.__class__.__name__} ({sum(component_count.values())} components)\n"
+
+        for component_type, number in component_count.items():
+            message += f"  - {component_type.value}: {number}\n"
+
+        return message
+
     def __new__(cls, *_args, **_kwargs):
         instance = super().__new__(cls)
         instance._model_ptr = ModelPtr()

tests/unit/test_power_grid_model.py

@@ -145,6 +145,11 @@ def model(input):
     return PowerGridModel(input)
 
 
+@pytest.fixture
+def empty_model():
+    return PowerGridModel({})
+
+
 def test_simple_power_flow(model: PowerGridModel, sym_output):
     result = model.calculate_power_flow()
     compare_result(result, sym_output, rtol=0.0, atol=1e-8)
@@ -176,11 +181,9 @@ def test_copy_model(model: PowerGridModel, sym_output):
     compare_result(result, sym_output, rtol=0.0, atol=1e-8)
 
 
-def test_deepcopy_model(model: PowerGridModel, sym_output, update_batch, sym_output_batch):
-    model_other = PowerGridModel({})
-
+def test_deepcopy_model(model: PowerGridModel, empty_model: PowerGridModel, sym_output, update_batch, sym_output_batch):
     # list containing different models twice
-    model_list = [model, model_other, model, model_other]
+    model_list = [model, empty_model, model, empty_model]
 
     new_model_list = deepcopy(model_list)
 
@@ -207,6 +210,16 @@ def test_deepcopy_model(model: PowerGridModel, sym_output, update_batch, sym_out
     compare_result(result, sym_output, rtol=0.0, atol=1e-8)
 
 
+def test_repr_and_str(model: PowerGridModel, empty_model: PowerGridModel):
+    repr_empty_model_expected = "PowerGridModel (0 components)\n"
+    assert repr_empty_model_expected == repr(empty_model)
+    assert repr_empty_model_expected == str(empty_model)
+
+    repr_model_expected = "PowerGridModel (3 components)\n  - node: 1\n  - source: 1\n  - sym_load: 1\n"
+    assert repr_model_expected == repr(model)
+    assert repr_model_expected == str(model)
+
+
 def test_get_indexer(model: PowerGridModel):
     ids = np.array([2, 2])
     expected_indexer = np.array([0, 0])