Make cim-graph and gridappsd-python optional dependencies

README.md

@@ -31,6 +31,17 @@ minimization, and generation curtailment minimization, where either generator re
 ```
 pip install distopf
 ```
+
+### Optional Extras
+
+| Extra | Install command | Purpose |
+|-------|----------------|---------|
+| `cim` | `pip install distopf[cim]` | CIM XML file import support (requires pre-release packages `cim-graph` and `gridappsd-python`) |
+
+> **Note:** The `cim` extra depends on pre-release packages. If you do not need CIM file support, a plain
+> `pip install distopf` is sufficient. CIM functionality will raise an informative `ImportError` if those
+> packages are not installed.
+
 ## Developer Installation
 To install the latest version from github:
 
@@ -43,6 +54,10 @@ To install the latest version from github:
 
 `pip install -e .`
 
+To also install the optional CIM extra in editable mode:
+
+`pip install -e ".[cim]"`
+
 This installs your local DistOPF package the python environment you activated. The `-e` option enables editable 
 mode, which allows you to directly edit the package and see changes immediately reflected in your environment 
 without reinstalling. 
@@ -342,6 +357,28 @@ case = opf.create_case(
 )
 ```
 
+# CIM XML Interface
+
+To load a power system model from a CIM XML file, install the optional `cim` extra first:
+
+```
+pip install distopf[cim]
+```
+
+Then pass the path to your `.xml` file:
+
+```python
+import distopf as opf
+case = opf.create_case(data_path="path/to/model.xml")
+```
+
+If the `cim` extra is not installed, calling `create_case` with a `.xml` file will raise:
+
+```
+ImportError: CIM file support requires optional dependencies.
+Install them with: pip install distopf[cim]
+```
+
 # Citing this tool
 
 Gray, Nathan T., Dubey, Anamika, Reiman, Andrew P., "DistOPF: Advanced Solutions for Distribution Optimal Power Flow Analysis - DistOPF v0.2 Documentation," (2025), https://doi.org/10.2172/2999990 

pyproject.toml

@@ -10,8 +10,6 @@ authors = [
 ]
 requires-python = ">=3.10"
 dependencies = [
-    "cim-graph==0.4.1a2",
-    "gridappsd-python==2025.3.2a13",
     "cvxpy>=1.7.2",
     "networkx>=3.4.2",
     "numpy>=2.2.6",
@@ -25,6 +23,12 @@ dependencies = [
     "highspy>=1.13.0",
 ]
 
+[project.optional-dependencies]
+cim = [
+    "cim-graph==0.4.1a2",
+    "gridappsd-python==2025.3.2a13",
+]
+
 [build-system]
 requires = ["hatchling"]
 build-backend = "hatchling.build"

src/distopf/api.py

@@ -1403,7 +1403,13 @@ def create_case_from_cim(
     try:
         # Lazy import to avoid loading cimgraph at module load time
         from distopf.cim_importer import CIMToCSVConverter
+    except ImportError as e:
+        raise ImportError(
+            "CIM file support requires optional dependencies. "
+            "Install them with: pip install distopf[cim]"
+        ) from e
 
+    try:
         cim_parser = CIMToCSVConverter(data_path)
         data = cim_parser.convert()
 

tests/cim_converter/conftest.py

@@ -0,0 +1,8 @@
+import pytest
+
+# Skip all CIM tests if the optional cim-graph dependency is not installed.
+# Install it with: pip install distopf[cim]
+pytest.importorskip(
+    "cimgraph",
+    reason="CIM tests require the 'cim' optional dependency: pip install distopf[cim]",
+)