Add Experiment.sorted_periods (#420)

Add `Experiment.sorted_periods` and extend tests.

Author: dweindl

petab/v2/core.py

@@ -631,6 +631,11 @@ def has_preequilibration(self) -> bool:
         """Check if the experiment has preequilibration enabled."""
         return any(period.is_preequilibration for period in self.periods)
 
+    @property
+    def sorted_periods(self) -> list[ExperimentPeriod]:
+        """Get the periods of the experiment sorted by time."""
+        return sorted(self.periods, key=lambda period: period.time)
+
     def sort_periods(self) -> None:
         """Sort the periods of the experiment by time."""
         self.periods.sort(key=lambda period: period.time)

tests/v2/test_core.py

@@ -10,7 +10,7 @@
 from sympy.abc import x, y
 
 import petab.v2 as petab
-from petab.v2 import Problem
+from petab.v2 import C, Problem
 from petab.v2.C import (
     CONDITION_ID,
     ESTIMATE,
@@ -256,18 +256,36 @@ def test_parameter():
 
 def test_experiment():
     Experiment(id="experiment1")
-    Experiment(
-        id="experiment1", periods=[ExperimentPeriod(time=1, condition_id="c1")]
-    )
 
+    # extra fields allowed
     assert Experiment(id="experiment1", non_petab=1).non_petab == 1
 
+    # ID required
     with pytest.raises(ValidationError, match="Field required"):
         Experiment()
 
+    # valid ID required
     with pytest.raises(ValidationError, match="Invalid ID"):
         Experiment(id="experiment 1")
 
+    periods = [
+        ExperimentPeriod(time=C.TIME_PREEQUILIBRATION, condition_ids=["c1"]),
+        ExperimentPeriod(time=-1, condition_id="c1"),
+        ExperimentPeriod(time=1, condition_id="c1"),
+    ]
+    e = Experiment(id="experiment1", periods=list(reversed(periods)))
+
+    assert e.has_preequilibration is True
+
+    assert e.sorted_periods == periods
+    assert e.periods != periods
+
+    e.sort_periods()
+    assert e.periods == periods
+
+    e.periods.pop(0)
+    assert e.has_preequilibration is False
+
 
 def test_condition_table():
     assert ConditionTable().free_symbols == set()