Micro-optimizations for Rotation methods

scipy/spatial/transform/_rotation.pyx

@@ -829,7 +829,10 @@ cdef class Rotation:
     @cython.wraparound(False)
     def __init__(self, quat, normalize=True, copy=True, scalar_first=False):
         self._single = False
-        quat = np.asarray(quat, dtype=float)
+        if normalize or copy:
+            quat = np.array(quat, copy=True, dtype=float)
+        else:
+            quat = np.asarray(quat, dtype=float)
 
         if quat.ndim not in [1, 2] or quat.shape[len(quat.shape) - 1] != 4:
             raise ValueError("Expected `quat` to have shape (4,) or (N, 4), "
@@ -846,8 +849,6 @@ cdef class Rotation:
 
         if scalar_first:
             quat = np.roll(quat, -1, axis=1)
-        elif normalize or copy:
-            quat = quat.copy()
 
         if normalize:
             for ind in range(num_rotations):
@@ -2699,9 +2700,9 @@ cdef class Rotation:
             return self.inv()
         elif n == 1:
             if self._single:
-                return self.__class__(self._quat[0], copy=True)
+                return self.__class__(self._quat[0], normalize=False, copy=True)
             else:
-                return self.__class__(self._quat, copy=True)
+                return self.__class__(self._quat, normalize=False, copy=True)
         else:  # general scaling of rotation angle
             return Rotation.from_rotvec(n * self.as_rotvec())
 
@@ -2744,7 +2745,7 @@ cdef class Rotation:
         quat[:, 2] *= -1
         if self._single:
             quat = quat[0]
-        return self.__class__(quat, copy=False)
+        return self.__class__(quat, normalize=False, copy=False)
 
     @cython.embedsignature(True)
     @cython.boundscheck(False)