question about matplotlib

qplot.py

# -*- coding: utf-8 -*-

import numpy as n
import random as r
import pylab as p

DIRS = ['up', 'right', 'down', 'left']

def new_guy():
    dna = [[r.choice(DIRS),
            r.randint(1, 40),
            1] for i in xrange(20)]
    return dna

def coords_guy(guy):
    x = 0
    y = 0
    xs = [0]
    ys = [0]
    for instr in guy:
        if instr[0] is 'up':
            y += instr[1] * instr[2]
        elif instr[0] is 'down':
            y -= instr[1] * instr[2]
        elif instr[0] is 'right':
            x += instr[1] * instr[2]
        elif instr[0] is 'left':
            print 'hey'
            x -= instr[1] * instr[2]
        xs.append(x)
        ys.append(y)
    return (xs, ys)

def guy_to_fig(guy):
    xs, ys = coords_guy(guy)

    p.clf()
    p.axis('off')
    p.plot(xs, ys, 'k-')
    p.savefig('guy.png')

guy_to_fig(new_guy())