Add support for gurobi installed via gurobipy from pip (#185)

Author: sebheger

.github/workflows/test.yml

@@ -78,7 +78,7 @@ jobs:
 
     - name: Install dependencies CPython
       if: ${{ matrix.python-version != 'pypy3' }}
-      run: python -m pip install cffi pytest networkx numpy matplotlib
+      run: python -m pip install cffi pytest networkx numpy matplotlib gurobipy
 
     - name: Install dependencies PyPy
       if: ${{ matrix.python-version == 'pypy3' && matrix.os != 'macos-latest' }}
@@ -94,7 +94,14 @@ jobs:
     - name: list installed packages
       run: python -m pip list
 
-    - name: run tests
+    - name: Run tests PyPy
+      if: ${{ matrix.python-version == 'pypy3'}}
+      run: |
+        python -m pytest test --verbose --color=yes --doctest-modules --ignore="test/test_gurobi.py"
+        python -m pytest mip --verbose --color=yes --doctest-modules --ignore="mip/gurobi.py"
+
+    - name: Run tests
+      if: ${{ matrix.python-version != 'pypy3'}}
       run: |
         python -m pytest test --verbose --color=yes --doctest-modules
         python -m pytest mip --verbose --color=yes --doctest-modules --ignore="mip/gurobi.py"

mip/gurobi.py

@@ -8,6 +8,8 @@
 from os import environ
 import numbers
 from cffi import FFI
+import importlib.util
+import pathlib
 from mip.exceptions import (
     ParameterNotAvailable,
     SolutionNotAvailable,
@@ -84,6 +86,18 @@
         if lib_path is not None:
             break
 
+# Check for gurobi 9.5 through pip installation
+if lib_path is None:
+    gurobipy_spec = importlib.util.find_spec("gurobipy")
+    if gurobipy_spec:
+        parent_path = pathlib.Path(gurobipy_spec.origin).parent
+        if platform.lower().startswith("win"):
+            extension = ".dll"
+        else:
+            extension = ".so"
+        lib_path = str(next(parent_path.glob(f"*{extension}")))
+
+
 if lib_path is None:
     found = False
 else:

test/test_gurobi.py

@@ -0,0 +1,12 @@
+import pytest
+
+import mip
+
+
+def test_gurobi_pip_installation():
+    # Even though we have no valid license yet, we could check that the binaries are found.
+    # If no valid license is found, an InterfacingError is thrown
+
+    with pytest.raises(mip.InterfacingError):
+        mip.Model(solver_name="GRB")
+