Add the ability to compare a timer to another value. (#13)

* Add the ability to compare a timer to another value.

This allows checking whether the last measured time is greater
or less than some 'reference' value.

This is useful if you want to display messages if some operation
has taken too long in the past.

* Use `last` for previous measurement

- also removes comparators, as timer.last can be used
  for comparison

* fix import sorting in tests

* sort imports in timer file

* relax the assertion of measured time in test

Author: janfreyberg

codetiming/_timer.py

@@ -5,9 +5,10 @@
 """
 
 # Standard library imports
+import time
 from contextlib import ContextDecorator
 from dataclasses import dataclass, field
-import time
+from math import nan
 from typing import Any, Callable, ClassVar, Dict, Optional
 
 
@@ -24,6 +25,7 @@ class Timer(ContextDecorator):
     text: str = "Elapsed time: {:0.4f} seconds"
     logger: Optional[Callable[[str], None]] = print
     _start_time: Optional[float] = field(default=None, init=False, repr=False)
+    last: float = field(default=nan, init=False, repr=False)
 
     def __post_init__(self) -> None:
         """Initialization: add timer to dict of timers"""
@@ -43,16 +45,16 @@ def stop(self) -> float:
             raise TimerError(f"Timer is not running. Use .start() to start it")
 
         # Calculate elapsed time
-        elapsed_time = time.perf_counter() - self._start_time
+        self.last = time.perf_counter() - self._start_time
         self._start_time = None
 
         # Report elapsed time
         if self.logger:
-            self.logger(self.text.format(elapsed_time))
+            self.logger(self.text.format(self.last))
         if self.name:
-            self.timers[self.name] += elapsed_time
+            self.timers[self.name] += self.last
 
-        return elapsed_time
+        return self.last
 
     def __enter__(self) -> "Timer":
         """Start a new timer as a context manager"""

tests/test_codetiming.py

@@ -4,14 +4,15 @@
 """
 # Standard library imports
 import re
+import time
+from math import isnan
 
 # Third party imports
 import pytest
 
 # Codetiming imports
 from codetiming import Timer, TimerError
 
-
 #
 # Test functions
 #
@@ -164,3 +165,13 @@ def test_error_if_restarting_running_timer():
     t.start()
     with pytest.raises(TimerError):
         t.start()
+
+
+def test_timer_sets_last():
+    t = Timer()
+    assert isnan(t.last)
+    t.start()
+    time.sleep(0.1)
+    t.stop()
+
+    assert 0.1 <= t.last