A Concise Introduction to Programming in Python

Chapter 6

Selection: If Statements

At both high levels and at the machine level, programs execute statements

one after the other. Selection statements allow a program to execute differ-

ent code depending on what happens as the program runs. This flexibility is

another key to the power of computation.

Listing 6.1: Centipede

1 # centipede.py

2

3 from turtle import

*

4

5 def centipede(length, step, life):

6 penup()

7 theta = 0

8 dtheta = 1

9 for i in range(life):

10 forward(step)

11 left(theta)

12 theta += dtheta

13 stamp()

14 if i > length:

15 clearstamps(1)

16 if theta > 10 or theta < -10:

17 dtheta = -dtheta

18 if ycor() > 350:

19 left(30)

20

21 def main():

22 setworldcoordinates(-400, ...