Euler to Quaternion transformation

transformations.py

from tf import transformations

# Docs for transformations.quaternion_from_euler
# You can get docs with transformations.quaternion_from_euler? and enter
#ai, aj, ak : Euler's roll, pitch and yaw angles
#axes : One of 24 axis sequences as string or encoded tuple
#q = quaternion_from_euler(1, 2, 3, 'ryxz')
#numpy.allclose(q, [0.310622, -0.718287, 0.444435, 0.435953])

transformations.quaternion_from_euler(0, 0, -1.550)
#Output: array([ 0.        ,  0.        , -0.69971608,  0.71442103])

You'll need to sudo apt-get install ros-groovy-tf and source /opt/ros/groovy/setup.bash first.