Fix pressure in dark sky and openweathermap and add pressure utility (#21210)

homeassistant/util/pressure.py

@@ -0,0 +1,51 @@
+"""Pressure util functions."""
+
+import logging
+from numbers import Number
+
+from homeassistant.const import (
+    PRESSURE_PA,
+    PRESSURE_HPA,
+    PRESSURE_MBAR,
+    PRESSURE_INHG,
+    PRESSURE_PSI,
+    UNIT_NOT_RECOGNIZED_TEMPLATE,
+    PRESSURE,
+)
+
+_LOGGER = logging.getLogger(__name__)
+
+VALID_UNITS = [
+    PRESSURE_PA,
+    PRESSURE_HPA,
+    PRESSURE_MBAR,
+    PRESSURE_INHG,
+    PRESSURE_PSI,
+]
+
+UNIT_CONVERSION = {
+    PRESSURE_PA: 1,
+    PRESSURE_HPA: 1 / 100,
+    PRESSURE_MBAR: 1 / 100,
+    PRESSURE_INHG: 1 / 3386.389,
+    PRESSURE_PSI: 1 / 6894.757,
+}
+
+
+def convert(value: float, unit_1: str, unit_2: str) -> float:
+    """Convert one unit of measurement to another."""
+    if unit_1 not in VALID_UNITS:
+        raise ValueError(
+            UNIT_NOT_RECOGNIZED_TEMPLATE.format(unit_1, PRESSURE))
+    if unit_2 not in VALID_UNITS:
+        raise ValueError(
+            UNIT_NOT_RECOGNIZED_TEMPLATE.format(unit_2, PRESSURE))
+
+    if not isinstance(value, Number):
+        raise TypeError('{} is not of numeric type'.format(value))
+
+    if unit_1 == unit_2 or unit_1 not in VALID_UNITS:
+        return value
+
+    pascals = value / UNIT_CONVERSION[unit_1]
+    return pascals * UNIT_CONVERSION[unit_2]