Add ruff linter

Author: sunqm

.github/workflows/lint.yml

@@ -0,0 +1,16 @@
+name: Lint
+
+on: [push, pull_request]
+
+jobs:
+  ruff:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v4
+    - name: Install ruff
+      run: pip install ruff
+    - name: Check style
+      run: ruff check --config .ruff.toml pyscf
+    - name: Check NumPy
+      run: ruff check --select NPY --ignore NPY002 pyscf

.ruff.toml

@@ -0,0 +1,32 @@
+exclude = [
+    "test",
+]
+
+respect-gitignore = true
+line-length = 120
+
+[lint]
+# Enable Pyflakes (`F`) and a subset of the pycodestyle (`E`)  codes by default.
+#select = ["E4", "E7", "E9", "F"]
+ignore = [
+# Whitespaces:
+"E201", "E202", "E203", "E211", "E221", "E222", "E225", "E226", "E228", "E231", "E241", "E251",
+# Comments:
+"E261", "E262", "E265", "E266",
+# Blank lines:
+"E301", "E302", "E303", "E305", "E306",
+# Imports:
+"E401", "E402",
+# Other:
+"E701", "E713", "E721", "E731", "E741", "E275",
+"F401", "F403", "C901", "W391"
+]
+
+[format]
+# Like Black, indent with spaces, rather than tabs.
+indent-style = "space"
+
+# Like Black, automatically detect the appropriate line ending.
+line-ending = "auto"
+
+quote-style = "single"

pyscf/dispersion/tests/test_d3.py

@@ -21,7 +21,7 @@
 def test_d3_unknown_xc():
     mol = pyscf.M(atom='H 0 0 0; H 0 0 1')
     with pytest.raises(RuntimeError):
-        model = DFTD3Dispersion(mol, xc='wb97x-v')
+        DFTD3Dispersion(mol, xc='wb97x-v')
 
 def test_d3_energy():
     mol = pyscf.M(atom='H 0 0 0; H 0 0 1')

pyscf/dispersion/tests/test_d4.py

@@ -21,7 +21,7 @@
 def test_d4_unknown_xc():
     mol = pyscf.M(atom='H 0 0 0; H 0 0 1')
     with pytest.raises(RuntimeError):
-        model = DFTD4Dispersion(mol, xc='wb97x-v')
+        DFTD4Dispersion(mol, xc='wb97x-v')
 
 def test_d4_energy():
     mol = pyscf.M(atom='H 0 0 0; H 0 0 1')

pyscf/dispersion/tests/test_gcp.py

@@ -22,7 +22,7 @@ def test_gcp_unknown_xc():
     mol = pyscf.M(atom='H 0 0 0; H 0 0 1')
     with pytest.raises(RuntimeError):
         model = GCP(mol, method='xx')
-        out = model.get_counterpoise()
+        model.get_counterpoise()
 
 def test_b973c_energy():
     mol = pyscf.M(atom='H 0 0 0; H 0 0 1')