1. turtle module Simple graphics programming How to use it ?
Import ‘turtle’ module by including
import turtle
Need to create a turtle, and NAME it to manipulate
Say, you named a turtle ‘xxx.’
xxx = Turtle() or Pen()
Opens up a turtle window
Can have more than one turtles at a time – tell them apart by names

2. turtle module >>> import turtle
>>> myT = turtle.Turtle()
What is “.” between turtle and Turtle() ?
turtle => class (generic object referring to turtle module)
Turtle() => method (action, function, constructor)
Rough interpretation: get ‘turtle’ type (class) and do ‘Turtle()’
>>> myT.color(“red”)
Get ‘myT’ turtle and color it red
Attribute
Position, heading (direction), color, tail position

3. Turtle in Python Actions References With myT
myT.forward(100), myT.backward(100)
myT.right(90), myT.left(45)
myT.goto(-200,90), myT.circle(50), myT.color(“red”)
myT.up(), myT.down()
myT.write(“Hello!”)
References
Official Python turtle page

4. Which methods to use ? Suppose ‘myT’ turtle is created
Draw a circle myT.circle(100)
Draw a thicker circle – myT.width(5)
Find out the location (x,y) of myT – myT.position()
Move myT to (100,-50) – myT.goto(100,-50)
Stop drawing – myT.up()
Find out the screen sizes
screen=myT.getscreen()
screen.window_width() and screen.window_height()

5. Iteration – drunken turle
Random walk or Brownian motion
A turtle
From the current position
Take an arbitrary direction and distance as the next position
Goto the next position
Next position becomes the current position next time around

6. Random package import random
random.randint(100) returns a random integer
How to get a random number between (0,100)?
A random number between (-50, 50) ?

7. Drunken Turtle With For loop
Create a turtle, name it on your own
For 200 times, repeat
Get the distance to the next random position from (curX, curY)
Add the distance to (curX, curY) to compute the new random location
Move the turtle to the new location

8. Drunken Turtle (curX, curY) = myT.position() for count in range(200):
For 200 times, repeat
Get the distance to the next random position from (curX, curY)
Add the distance to (curX, curY) to compute the new random location
Move the turtle to the new location
(curX, curY) = myT.position()
for count in range(200):
newX = curX + random.randint(-50,50)
newY = curY + random.randint(-50,50)
myT.goto(newX, newY)
curX = newX
curY = newY

9. Drunken Turtle Same variable can be replaced by a new updated value
(curX, curY) = myT.position()
for count in range(200):
newX = curX + random.randint(-50,50)
newY = curY + random.randint(-50,50)
myT.goto(newX, newY)
curX = newX
curY = newY
curX curY rand_X rand_Y newX newY

10. Drunken Turtle Same variable can be replaced by a new updated value
(curX, curY) = myT.position()
for count in range(200):
newX = curX + random.randint(-50,50)
newY = curY + random.randint(-50,50)
myT.goto(newX, newY)
curX = newX
curY = newY
(curX, curY) = myT.position()
for count in range(200):
curX = curX + random.randint(-50,50)
curY = curY + random.randint(-50,50)
myT.goto(curX, curY)

11. Keep Turtle in-bound Window bounds win = myT.getscreen()
wWid = win.window_width()
wHgt = win.window_height()
winRight = int(wWid/2)
winLeft = -winRight
winTop =int(wHgt/2)
winBottom = -winTop

12. Keep Turtle in-bound Updated position at (curX, curY)
If curX > winRight
If curX < winLeft
If curY > winTop
If curY < winBottom

13. Lab 0921
Write a Python program to simulate a drunken turtle for 500 random walks.
Modify the drunken turtle program so that the turtle stays in bound
your Python program to