Improve the performance of dt_util.utcnow() (#39145)

homeassistant/util/dt.py

@@ -52,7 +52,7 @@ def get_time_zone(time_zone_str: str) -> Optional[dt.tzinfo]:
 
 def utcnow() -> dt.datetime:
     """Get now in UTC time."""
-    return dt.datetime.now(UTC)
+    return dt.datetime.utcnow().replace(tzinfo=UTC)
 
 
 def now(time_zone: Optional[dt.tzinfo] = None) -> dt.datetime:

tests/components/metoffice/__init__.py

@@ -1 +1,12 @@
 """Tests for the metoffice component."""
+
+import datetime
+
+
+class NewDateTime(datetime.datetime):
+    """Patch time to a specific point."""
+
+    @classmethod
+    def now(cls, *args, **kwargs):  # pylint: disable=signature-differs
+        """Overload datetime.datetime.now."""
+        return cls(2020, 4, 25, 12, tzinfo=datetime.timezone.utc)

tests/components/metoffice/test_sensor.py

@@ -1,9 +1,9 @@
 """The tests for the Met Office sensor component."""
-from datetime import datetime, timezone
 import json
 
 from homeassistant.components.metoffice.const import ATTRIBUTION, DOMAIN
 
+from . import NewDateTime
 from .const import (
     DATETIME_FORMAT,
     KINGSLYNN_SENSOR_RESULTS,
@@ -15,13 +15,12 @@ from .const import (
     WAVERTREE_SENSOR_RESULTS,
 )
 
-from tests.async_mock import Mock, patch
+from tests.async_mock import patch
 from tests.common import MockConfigEntry, load_fixture
 
 
 @patch(
-    "datapoint.Forecast.datetime.datetime",
-    Mock(now=Mock(return_value=datetime(2020, 4, 25, 12, tzinfo=timezone.utc))),
+    "datapoint.Forecast.datetime.datetime", NewDateTime,
 )
 async def test_one_sensor_site_running(hass, requests_mock, legacy_patchable_time):
     """Test the Met Office sensor platform."""
@@ -58,8 +57,7 @@ async def test_one_sensor_site_running(hass, requests_mock, legacy_patchable_tim
 
 
 @patch(
-    "datapoint.Forecast.datetime.datetime",
-    Mock(now=Mock(return_value=datetime(2020, 4, 25, 12, tzinfo=timezone.utc))),
+    "datapoint.Forecast.datetime.datetime", NewDateTime,
 )
 async def test_two_sensor_sites_running(hass, requests_mock, legacy_patchable_time):
     """Test we handle two sets of sensors running for two different sites."""

tests/components/metoffice/test_weather.py

@@ -1,24 +1,24 @@
 """The tests for the Met Office sensor component."""
-from datetime import datetime, timedelta, timezone
+from datetime import timedelta
 import json
 
 from homeassistant.components.metoffice.const import DOMAIN
 from homeassistant.const import STATE_UNAVAILABLE
 from homeassistant.util import utcnow
 
+from . import NewDateTime
 from .const import (
     METOFFICE_CONFIG_KINGSLYNN,
     METOFFICE_CONFIG_WAVERTREE,
     WAVERTREE_SENSOR_RESULTS,
 )
 
-from tests.async_mock import Mock, patch
+from tests.async_mock import patch
 from tests.common import MockConfigEntry, async_fire_time_changed, load_fixture
 
 
 @patch(
-    "datapoint.Forecast.datetime.datetime",
-    Mock(now=Mock(return_value=datetime(2020, 4, 25, 12, tzinfo=timezone.utc))),
+    "datapoint.Forecast.datetime.datetime", NewDateTime,
 )
 async def test_site_cannot_connect(hass, requests_mock, legacy_patchable_time):
     """Test we handle cannot connect error."""
@@ -39,8 +39,7 @@ async def test_site_cannot_connect(hass, requests_mock, legacy_patchable_time):
 
 
 @patch(
-    "datapoint.Forecast.datetime.datetime",
-    Mock(now=Mock(return_value=datetime(2020, 4, 25, 12, tzinfo=timezone.utc))),
+    "datapoint.Forecast.datetime.datetime", NewDateTime,
 )
 async def test_site_cannot_update(hass, requests_mock, legacy_patchable_time):
     """Test we handle cannot connect error."""
@@ -74,8 +73,7 @@ async def test_site_cannot_update(hass, requests_mock, legacy_patchable_time):
 
 
 @patch(
-    "datapoint.Forecast.datetime.datetime",
-    Mock(now=Mock(return_value=datetime(2020, 4, 25, 12, tzinfo=timezone.utc))),
+    "datapoint.Forecast.datetime.datetime", NewDateTime,
 )
 async def test_one_weather_site_running(hass, requests_mock, legacy_patchable_time):
     """Test the Met Office weather platform."""
@@ -108,8 +106,7 @@ async def test_one_weather_site_running(hass, requests_mock, legacy_patchable_ti
 
 
 @patch(
-    "datapoint.Forecast.datetime.datetime",
-    Mock(now=Mock(return_value=datetime(2020, 4, 25, 12, tzinfo=timezone.utc))),
+    "datapoint.Forecast.datetime.datetime", NewDateTime,
 )
 async def test_two_weather_sites_running(hass, requests_mock, legacy_patchable_time):
     """Test we handle two different weather sites both running."""