Python < 3.9 can't handle case statement.

.github/workflows/python-test.yml

@@ -30,6 +30,12 @@ jobs:
         python -m pip install --upgrade pip
         python -m pip install flake8 pytest
         python -m pip install -r requirements.txt
+    - name: Lint with flake8
+      run: |
+        # stop the build if there are Python syntax errors or undefined names
+        flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
+        # exit-zero treats all errors as warnings. The GitHub editor is 127 chars wide
+        flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
     - name: Test with pytest
       run: |
         python -m pytest tests --timesensitive

graph/tsp.py

@@ -255,22 +255,21 @@ def reverse_segment_if_better(tour, i, j, k):
         best = [(a, b) for a, b in zip([d0, d1, d2, d3, d4], ["d0", "d1", "d2", "d3", "d4"])]
         best.sort()
         _, index = best[0]
-        match index:
-            case "d1":
-                tour[i:j] = reversed(tour[i:j])
-                return -d0 + d1
-            case "d2":
-                tour[j:k] = reversed(tour[j:k])
-                return -d0 + d2
-            case "d3":
-                tmp = tour[j:k] + tour[i:j]
-                tour[i:k] = tmp
-                return -d0 + d3
-            case "d4":
-                tour[i:k] = reversed(tour[i:k])
-                return -d0 + d4
-            case _:
-                return 0
+        if index == "d1":
+            tour[i:j] = reversed(tour[i:j])
+            return -d0 + d1
+        elif index == "d2":
+            tour[j:k] = reversed(tour[j:k])
+            return -d0 + d2
+        elif index == "d3":
+            tmp = tour[j:k] + tour[i:j]
+            tour[i:k] = tmp
+            return -d0 + d3
+        elif index == "d4":
+            tour[i:k] = reversed(tour[i:k])
+            return -d0 + d4
+        else:
+            return 0
 
     def all_segments(n: int):
         """Generate all segments combinations"""