Axis-Angle->Euler Conversion

#!/usr/bin/env python

import math
import sys


def aa2e(axis_angle):
	axis = axis_angle[:-1]
	angle = axis_angle[-1]
	quat = [q * math.cos(angle/2) for q in axis] + [math.sin(angle/2)]
	s, t = math.sin(angle), 1 - math.cos(angle)
	x,y,z=axis
	z_comp = x * y * t + z * s
	if abs(z_comp) > 0.999: # singularity up north
		sign = cmp(z_comp, 0)
		bank = 0
		heading = sign * 2 * math.atan2(x * math.sin(angle/2),math.cos(angle/2))
		attitude = sign * math.pi/2
	else:
		bank = math.atan2(x * s - y * z * t , 1 - (x**2 + z**2) * t)
		heading = math.atan2(y * s - x * z * t , 1 - (y**2+ z**2 ) * t)
		attitude = math.asin(z_comp) 
	return (bank, heading, attitude)

if __name__ == "__main__":
	print "(%.7f %.7f %.7f)" % aa2e([float(i) for i in sys.argv[1:5]])

Quote:
[thomas@Bombadil] ~ $ axisangle_to_euler.py 0.707 0.707 0 3.14
(0.0000000 3.1393400 1.5707963)