Made compatible to Python 3.9

setup.py

@@ -22,48 +22,47 @@ def find_sources(exclude_from_compilation):
 
 
 compiler = os.environ.get('SETUP_BUILD_EXTENSION', "False").capitalize()
-match compiler:
-    case "False":
-        print("\nsetup.py: Building sdist (tarball) / and or pure Python wheel.")
-        print("(Set environment variable SETUP_BUILD_EXTENSION to MyPyC or Cython "
-              "to compile binaries.)")
-        ext_modules = []
+if compiler == "False":
+    print("\nsetup.py: Building sdist (tarball) / and or pure Python wheel.")
+    print("(Set environment variable SETUP_BUILD_EXTENSION to MyPyC or Cython "
+          "to compile binaries.)")
+    ext_modules = []
 
-    case "Mypyc":
-        print(f"\nsetup.py: Compiling binaries using MyPyC.")
-        print("(Set environment variable SETUP_BUILD_EXTENSION to False "
-              "to build sdist / and or pure Python wheel instead.)")
-
-        from mypyc.build import mypycify
-        exclude_from_compilation = [
-            # The following file contains classes, compilation would be useful, but
-            # it is intentionally not compiled here due to the following issue of
-            # MyPyC:
-            # https://github.com/mypyc/mypyc/issues/1022
-            'depth_first_enum_types.py',
-            # The following file subclasses tuple[int]. MyPyC does not support this.
-            # But on CPython this us much faster than to store the tuple in an attribute
-            # Conditional class definition is also not supported. So, we simply exclude
-            # this file from compilation.
-            '_extra_matrix_gadgets.py',
-        ]
-        compile_this = find_sources(exclude_from_compilation)
-        ext_modules = mypycify(compile_this, strip_asserts=False)
+elif compiler == "Mypyc":
+    print(f"\nsetup.py: Compiling binaries using MyPyC.")
+    print("(Set environment variable SETUP_BUILD_EXTENSION to False "
+          "to build sdist / and or pure Python wheel instead.)")
 
-    case "Cython":
-        print(f"\nsetup.py: Compiling binaries using Cython.")
-        print("(Set environment variable SETUP_BUILD_EXTENSION to False "
-              "to build sdist / and or pure Python wheel instead.)")
-        from Cython.Build import cythonize
-        exclude_from_compilation = []
-        compile_this = find_sources(exclude_from_compilation)
-        ext_modules = cythonize(compile_this, compiler_directives={'language_level': 3})
+    from mypyc.build import mypycify
+    exclude_from_compilation = [
+        # The following file contains classes, compilation would be useful, but
+        # it is intentionally not compiled here due to the following issue of
+        # MyPyC:
+        # https://github.com/mypyc/mypyc/issues/1022
+        'depth_first_enum_types.py',
+        # The following file subclasses tuple[int]. MyPyC does not support this.
+        # But on CPython this us much faster than to store the tuple in an attribute
+        # Conditional class definition is also not supported. So, we simply exclude
+        # this file from compilation.
+        '_extra_matrix_gadgets.py',
+    ]
+    compile_this = find_sources(exclude_from_compilation)
+    ext_modules = mypycify(compile_this, strip_asserts=False)
 
-    case _:
-        raise RuntimeError(
-            "Valid values or environment variable SETUP_BUILD_EXTENSION are:"
-            "  'False', 'MyPyC', and 'Cython'"
-            "If no value is set, this equals to 'False'.")
+elif compiler == "Cython":
+    print(f"\nsetup.py: Compiling binaries using Cython.")
+    print("(Set environment variable SETUP_BUILD_EXTENSION to False "
+          "to build sdist / and or pure Python wheel instead.)")
+    from Cython.Build import cythonize
+    exclude_from_compilation = []
+    compile_this = find_sources(exclude_from_compilation)
+    ext_modules = cythonize(compile_this, compiler_directives={'language_level': 3})
+
+else:
+    raise RuntimeError(
+        "Valid values or environment variable SETUP_BUILD_EXTENSION are:"
+        "  'False', 'MyPyC', and 'Cython'"
+        "If no value is set, this equals to 'False'.")
 
 if ext_modules:
     setup(