Add helper function for computing a duration from timeMethod output

python/lsst/utils/timer.py

@@ -14,7 +14,7 @@
 
 from __future__ import annotations
 
-__all__ = ["profile", "logInfo", "timeMethod", "time_this"]
+__all__ = ["duration_from_timeMethod", "profile", "logInfo", "timeMethod", "time_this"]
 
 import datetime
 import functools
@@ -479,3 +479,33 @@ def profile(filename: str | None, log: LsstLoggers | None = None) -> Iterator[cP
     profile.dump_stats(filename)
     if log is not None:
         log.info("cProfile stats written to %s", filename)
+
+
+def duration_from_timeMethod(
+    metadata: MutableMapping | None, method_name: str, clock: str = "Cpu"
+) -> float | None:
+    """Parse the metadata entries from ``timeMethod`` and return a duration
+
+    Parameters
+    ----------
+    metadata : `collections.abc.MutableMapping`
+        The Task metadata that timing metrics were added to.
+    method_name : `str`
+        Name of the timed method to extract a duration for.
+    clock : `str`, optional
+        Options are "Cpu", "User", or "System"
+
+    Returns
+    -------
+    duration : `float`
+        The time elapsed between the start and end of the timed method.
+    """
+    if metadata is None:
+        return None
+    start = metadata[method_name + "Start" + clock + "Time"]
+    if isinstance(start, list):
+        start = start[-1]
+    end = metadata[method_name + "End" + clock + "Time"]
+    if isinstance(end, list):
+        end = end[-1]
+    return end - start

tests/test_timer.py

@@ -29,7 +29,7 @@
 from dataclasses import dataclass
 
 from astropy import units as u
-from lsst.utils.timer import logInfo, logPairs, profile, time_this, timeMethod
+from lsst.utils.timer import duration_from_timeMethod, logInfo, logPairs, profile, time_this, timeMethod
 
 log = logging.getLogger("test_timer")
 
@@ -164,6 +164,9 @@ def testTaskLike(self):
             with self.subTest(log=log, metadata=metadata):
                 task = Example1(log=log, metadata=metadata)
                 self.assertTimer(duration, task)
+                exampleDuration = duration_from_timeMethod(task.metadata, "sleeper")
+                if metadata is not None:
+                    self.assertGreater(exampleDuration, 0)
 
     def testDecorated(self):
         """Test timeMethod on non-Task like instances."""