From 0a11acf7aed62ce8f76a6fd76bda1dacc89d8a0f Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Sat, 7 Sep 2024 22:49:44 -0500
Subject: [PATCH] Replace linear search in unit_system with dict lookup
 (#125485)

---
 homeassistant/util/unit_system.py | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/homeassistant/util/unit_system.py b/homeassistant/util/unit_system.py
index bd31b4286ab..98cfb2f1368 100644
--- a/homeassistant/util/unit_system.py
+++ b/homeassistant/util/unit_system.py
@@ -58,23 +58,21 @@ WIND_SPEED_UNITS = SpeedConverter.VALID_UNITS
 
 TEMPERATURE_UNITS: set[str] = {UnitOfTemperature.FAHRENHEIT, UnitOfTemperature.CELSIUS}
 
+_VALID_BY_TYPE: dict[str, set[str] | set[str | None]] = {
+    LENGTH: LENGTH_UNITS,
+    ACCUMULATED_PRECIPITATION: LENGTH_UNITS,
+    WIND_SPEED: WIND_SPEED_UNITS,
+    TEMPERATURE: TEMPERATURE_UNITS,
+    MASS: MASS_UNITS,
+    VOLUME: VOLUME_UNITS,
+    PRESSURE: PRESSURE_UNITS,
+}
+
 
 def _is_valid_unit(unit: str, unit_type: str) -> bool:
     """Check if the unit is valid for it's type."""
-    if unit_type == LENGTH:
-        return unit in LENGTH_UNITS
-    if unit_type == ACCUMULATED_PRECIPITATION:
-        return unit in LENGTH_UNITS
-    if unit_type == WIND_SPEED:
-        return unit in WIND_SPEED_UNITS
-    if unit_type == TEMPERATURE:
-        return unit in TEMPERATURE_UNITS
-    if unit_type == MASS:
-        return unit in MASS_UNITS
-    if unit_type == VOLUME:
-        return unit in VOLUME_UNITS
-    if unit_type == PRESSURE:
-        return unit in PRESSURE_UNITS
+    if units := _VALID_BY_TYPE.get(unit_type):
+        return unit in units
     return False