Hello, 

The most obvious disadvantage of this approach ( though there may be others ) is that that you need to use a delegate method 'Q' to get at Sketch variables ( which are available in processing.py if I understand correctly by setting them as built-ins before invoking the draw method of your Sketch ). So it's marginally more difficult to translate standard Processing code.

Still you can get pretty far with import tricks, here is some sample code ( from Daniel Schiffman's Tree example ): 

# Recursive Tree

# by Daniel Shiffman.

# Renders a simple tree-like structure via recursion.

# The branching angle is calculated as a function of

# the horizontal mouse location. Move the mouse left

# and right to change the angle.

from jocelyn import *

class mem:

    theta = None

class TreeSketch(Sketch):

    def setup(self):

        size(640, 360)

    def draw(self):

        background(0)

        frameRate(30)

        stroke(255)

        a = Q('mouseX') / Q('width') * 90

        mem.theta = float(radians(a))

        translate(Q('width')/2,Q('height'))

        line(0,0,0,-120)

        translate(0,-120)

        # Start the recursive branching!

        branch(120)

def branch(h):

    #Each branch will be 2/3rds the size of the previous one

    h = h *0.66

    # All recursive functions must have an exit condition!!!!

    # Here, ours is when the length of the branch is 2 pixels or less

    if (h > 2):

        pushMatrix() # Save the current state of transformation (i.e. where are we now)

        rotate(mem.theta) # Rotate by theta

        line(0, 0, 0, -h) # Draw the branch

        translate(0, -h) # Move to the end of the branch

        branch(h) # Ok, now call myself to draw two new branches!!

        popMatrix() # Whenever we get back here, we "pop" in order to restore the previous matrix state

        #Repeat the same thing, only branch off to the "left" this time!

        pushMatrix()

        rotate(-mem.theta)

        line(0, 0, 0, -h)

        translate(0, -h)

        branch(h)

        popMatrix()

if __name__ == '__main__':

    TreeSketch().run_sketch()