Support pickling a linopy model (#438)

Author: victorgarcia98

doc/release_notes.rst

@@ -13,6 +13,10 @@ Version 0.5.2
 This is mainly affecting operations where single numerical items from  pandas objects
 are selected and used for multiplication.
 
+**Feature**
+
+* Support pickling models.
+
 Version 0.5.1
 --------------
 

linopy/constraints.py

@@ -756,6 +756,12 @@ def __getattr__(self, name: str) -> Constraint:
             f"Constraints has no attribute `{name}` or the attribute is not accessible, e.g. raises an error."
         )
 
+    def __getstate__(self) -> dict:
+        return self.__dict__
+
+    def __setstate__(self, d: dict) -> None:
+        self.__dict__.update(d)
+
     def __dir__(self) -> list[str]:
         base_attributes = list(super().__dir__())
         formatted_names = [

linopy/variables.py

@@ -1182,6 +1182,12 @@ def __getattr__(self, name: str) -> Variable:
             f"Variables has no attribute `{name}` or the attribute is not accessible / raises an error."
         )
 
+    def __getstate__(self) -> dict:
+        return self.__dict__
+
+    def __setstate__(self, d: dict) -> None:
+        self.__dict__.update(d)
+
     def __dir__(self) -> list[str]:
         base_attributes = list(super().__dir__())
         formatted_names = [

test/test_io.py

@@ -5,6 +5,7 @@
 @author: fabian
 """
 
+import pickle
 from pathlib import Path
 from typing import Union
 
@@ -109,6 +110,21 @@ def test_model_to_netcdf_with_status_and_condition(
     assert_model_equal(m, p)
 
 
+def test_pickle_model(model_with_dash_names: Model, tmp_path: Path) -> None:
+    m = model_with_dash_names
+    fn = tmp_path / "test.nc"
+    m._status = "ok"
+    m._termination_condition = "optimal"
+
+    with open(fn, "wb") as f:
+        pickle.dump(m, f)
+
+    with open(fn, "rb") as f:
+        p = pickle.load(f)
+
+    assert_model_equal(m, p)
+
+
 # skip it xarray version is 2024.01.0 due to issue https://github.com/pydata/xarray/issues/8628
 @pytest.mark.skipif(
     xr.__version__ in ["2024.1.0", "2024.1.1"],