import mathutils
import math

# A new rotation 90 degrees about the Y axis.
quat_a = mathutils.Quaternion((0.7071068, 0.0, 0.7071068, 0.0))

# Passing values to Quaternion's directly can be confusing so axis, angle
# is supported for initializing too.
quat_b = mathutils.Quaternion((0.0, 1.0, 0.0), math.radians(90.0))

print("Check quaternions match", quat_a == quat_b)

# Like matrices, quaternions can be multiplied to accumulate rotational values.
quat_a = mathutils.Quaternion((0.0, 1.0, 0.0), math.radians(90.0))
quat_b = mathutils.Quaternion((0.0, 0.0, 1.0), math.radians(45.0))
quat_out = quat_a @ quat_b

# Print the quaternion, euler degrees for mere mortals and (axis, angle).
print("Final Rotation:")
print(quat_out)
print("{:.2f}, {:.2f}, {:.2f}".format(*(math.degrees(a) for a in quat_out.to_euler())))
print("({:.2f}, {:.2f}, {:.2f}), {:.2f}".format(*quat_out.axis, math.degrees(quat_out.angle)))

# Multiple rotations can be interpolated using the exponential map.
quat_c = mathutils.Quaternion((1.0, 0.0, 0.0), math.radians(15.0))
exp_avg = (quat_a.to_exponential_map() +
           quat_b.to_exponential_map() +
           quat_c.to_exponential_map()) / 3.0
quat_avg = mathutils.Quaternion(exp_avg)
print("Average rotation:")
print(quat_avg)
