Add get_mid_price

betfairutil/__init__.py

@@ -1827,6 +1827,15 @@ def get_best_price_size(
         return next(iter(runner.get("ex", {}).get(side.ex_key, [])), None)
 
 
+def get_mid_price(
+    runner: Union[Dict[str, Any], RunnerBook]
+) -> Optional[Union[int, float]]:
+    best_back = get_best_price(runner, Side.BACK)
+    best_lay = get_best_price(runner, Side.LAY)
+    if best_back is not None and best_lay is not None:
+        return (best_back + best_lay) / 2
+
+
 def get_best_price(
     runner: Union[Dict[str, Any], RunnerBook], side: Side
 ) -> Optional[Union[int, float]]:

tests/test_non_prices.py

@@ -39,6 +39,7 @@
 from betfairutil import get_market_books_from_prices_file
 from betfairutil import get_market_id_from_string
 from betfairutil import get_market_time_as_datetime
+from betfairutil import get_mid_price
 from betfairutil import get_minimum_book_percentage_market_books_from_prices_file
 from betfairutil import get_number_of_jumps_remaining
 from betfairutil import get_pre_event_volume_traded_from_prices_file
@@ -1232,3 +1233,11 @@ def test_get_number_of_jumps_remaining(race_change: Dict[str, Any]):
     race_change["rpc"]["J"] = [{"L": 1000}]
     number_of_jumps_remaining = get_number_of_jumps_remaining(race_change)
     assert number_of_jumps_remaining == 1
+
+
+def test_get_mid_price(market_book: Dict[str, Any]):
+    runner_book = get_runner_book_from_market_book(market_book, selection_id=123)
+    assert get_mid_price(runner_book) is None
+
+    runner_book["ex"]["availableToLay"].append({"price": 1.99, "size": 1})
+    assert get_mid_price(runner_book) == pytest.approx(1.985)