Doc: match statement in style guide (#5187)

* Test: add micro benchmark for match

* Doc: add 'match' to python style guide

docs/style.md

@@ -29,6 +29,10 @@
 * New classes, attributes, and methods in core code should have docstrings that follow
   [reST style](https://peps.python.org/pep-0287/).
 * Worlds that do not follow PEP8 should still have a consistent style across its files to make reading easier.
+* [Match statements](https://docs.python.org/3/tutorial/controlflow.html#tut-match)
+  may be used instead of `if`-`elif` if they result in nicer code, or they actually use pattern matching.
+  Beware of the performance: they are not `goto`s, but `if`-`elif` under the hood, and you may have less control. When
+  in doubt, just don't use it.
 
 ## Markdown
 

test/benchmark/match.py

@@ -0,0 +1,66 @@
+"""Micro benchmark comparing match as "switch" with if-elif and dict access"""
+
+from timeit import timeit
+
+
+def make_match(count: int) -> str:
+    code = f"for val in range({count}):\n    match val:\n"
+    for n in range(count):
+        m = n + 1
+        code += f"        case {n}:\n"
+        code += f"            res = {m}\n"
+    return code
+
+
+def make_elif(count: int) -> str:
+    code = f"for val in range({count}):\n"
+    for n in range(count):
+        m = n + 1
+        code += f"    {'' if n == 0 else 'el'}if val == {n}:\n"
+        code += f"        res = {m}\n"
+    return code
+
+
+def make_dict(count: int, mode: str) -> str:
+    if mode == "value":
+        code = "dct = {\n"
+        for n in range(count):
+            m = n + 1
+            code += f"    {n}: {m},\n"
+        code += "}\n"
+        code += f"for val in range({count}):\n    res = dct[val]"
+        return code
+    elif mode == "call":
+        code = ""
+        for n in range(count):
+            m = n + 1
+            code += f"def func{n}():\n    val = {m}\n\n"
+        code += "dct = {\n"
+        for n in range(count):
+            code += f"    {n}: func{n},\n"
+        code += "}\n"
+        code += f"for val in range({count}):\n    dct[val]()"
+        return code
+    return ""
+
+
+def timeit_best_of_5(stmt: str, setup: str = "pass") -> float:
+    """
+    Benchmark some code, returning the best of 5 runs.
+    :param stmt: Code to benchmark
+    :param setup: Optional code to set up environment
+    :return: Time taken in microseconds
+    """
+    return min(timeit(stmt, setup, number=10000, globals={}) for _ in range(5)) * 100
+
+
+def main() -> None:
+    for count in (3, 5, 8, 10, 20, 30):
+        print(f"value of {count:-2} with match: {timeit_best_of_5(make_match(count)) / count:.3f} us")
+        print(f"value of {count:-2} with elif:  {timeit_best_of_5(make_elif(count)) / count:.3f} us")
+        print(f"value of {count:-2} with dict:  {timeit_best_of_5(make_dict(count, 'value')) / count:.3f} us")
+        print(f"call  of {count:-2} with dict:  {timeit_best_of_5(make_dict(count, 'call')) / count:.3f} us")
+
+
+if __name__ == "__main__":
+    main()