Handle EnforcePatternOccurence parameters

dnachisel/builtin_specifications/EnforcePatternOccurence.py

@@ -63,19 +63,25 @@ def __init__(
             pattern = SequencePattern.from_string(pattern)
         self.pattern = pattern
         self.location = Location.from_data(location)
-        if strand != "from_location":
-            if strand == "both":
-                strand = 0
-            if strand not in [-1, 0, 1]:
-                raise ValueError("unknown strand: %s" % strand)
-            self.location.strand = strand
-        self.strand = strand
+        if strand == "from_location":
+            if self.location is None:
+                self.strand = 0
+            else:
+                self.strand = self.location.strand
+        elif strand == "both":
+            self.strand = 0
+        elif strand in [-1, 0, 1]:
+            self.strand = strand
+        else:
+            raise ValueError("unknown strand: %s" % strand)
         self.occurences = occurences
         self.center = center
         self.boost = boost
 
     def initialized_on_problem(self, problem, role=None):
-        return self._copy_with_full_span_if_no_location(problem)
+        copy_of_constraint = self._copy_with_full_span_if_no_location(problem)
+        copy_of_constraint.location.strand = self.strand
+        return copy_of_constraint
 
     def evaluate(self, problem):
         """Score the difference between expected and observed n_occurences."""

tests/builtin_specifications/test_EnforcePatternOccurence.py

@@ -28,9 +28,7 @@ def test_enforce_pattern_basics():
         constraints = [
             EnforceTranslation(location=Location(1000, 2500)),
             EnforceTranslation(location=Location(3000, 4500)),
-            EnforcePatternOccurence(
-                "ANANANANTT", location=Location(1100, 2150)
-            ),
+            EnforcePatternOccurence("ANANANANTT", location=Location(1100, 2150)),
         ]
 
         problem = DnaOptimizationProblem(