Add constant multiplication on trajectories

tests/test_trajectory/test_operations.py

@@ -47,7 +47,7 @@ def test_iteration(points, angles, traj):
         assert ang == approx(tp.ang, APPROX_REL_TOLERANCE)  # Angle
 
 
-def test_contant_addition(points, traj):
+def test_constant_addition(points, traj):
     new_traj = traj + 10
     new_points = points + 10
 
@@ -77,7 +77,7 @@ def test_wrong_addition(traj):
         traj += 'wrong'
 
 
-def test_contant_substraction(points, traj):
+def test_constant_substraction(points, traj):
     new_traj = traj - 10
     new_points = points - 10
 
@@ -105,3 +105,18 @@ def test_traj_substraction(points, traj):
 def test_wrong_substraction(traj):
     with pytest.raises(TypeError):
         traj -= 'wrong'
+
+
+def test_constant_multiplication(points, traj):
+    new_traj = traj * 3
+    new_points = points * 3
+
+    for true_point, point in zip(new_points, new_traj.r):
+        assert true_point == approx(point, APPROX_REL_TOLERANCE)
+
+
+def test_wrong_multiplication(traj):
+    with pytest.raises(TypeError):
+        traj *= 'wrong'
+    with pytest.raises(TypeError):
+        traj *= [1, 2]

yupi/trajectory.py

@@ -387,6 +387,22 @@ def __radd__(self, other):
     def __rsub__(self, other):
         return self - other
 
+    def __imul__(self, other):
+        if isinstance(other, (int, float)):
+            self.r *= other
+            return self
+
+        raise TypeError("unsoported operation (*) between 'Trajectory' and "
+                        f"'{type(other).__name__}'")
+
+    def __mul__(self, other):
+        traj = self.copy()
+        traj *= other
+        return traj
+
+    def __rmul__(self, other):
+        return self * other
+
     def _save_json(self, path: str):
         def convert_to_list(vec: Vector):
             if vec is None: