turtle graphics victor norman cs104 calvin college
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Turtle Graphics
Victor NormanCS104
Calvin College
Reading Quiz
• Counts toward your grade.
Quick Introduction to Objects
• You have to instantiate the object, making a variable refer to it:– turt = turtle.Turtle()
• You call (or "invoke") methods on it:– turt.forward(10)– turt.doSomething(33, 22, 11)
• It is like asking the object to do something to itself: give me back a value or move yourself, or draw something, or change a value.
• The object stores its own state (or characteristics, properties, or attributes).
Clicker Question
for Loop Syntax
• Pattern:for <var> in <sequence>:
<body> # multiple statements
• Examples:for aVal in [3, 11, 22, 0, -3]:
print(aVal)for aVal in [“I’m”, “a”, “lumberjack”, “and”,
“I’m”, “ok”, 8, math.pi]:
print(aVal)
for Loop Examplesfor val in [0, 1, 2, 3, 4, 5]:
turt.forward(50)turt.left(60)
total = 0for val in [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]:
total = total + valprint(total)
total = 0for val in range(1, 21):
total = total + valprint(total)
range(start, stop, step)
• Built-in function• Generates list of integers starting at start,
going up to (but not including) stop, by increments of step.
• Can skip start uses 0. E.g., range(10)• Can skip step uses 1. E.g., range(3, 7)
range() Examples
range(30)• generates list of numbers 0, 1, 2, …, 29.range(2, 30)• generates list of numbers 2, 3, 4, 5, …, 29.range(-3, 3, 2)• generates list of numbers -3, -1, 1.range(20, 0, -1)• generates list of numbers 20, 19, 18, 17, …, 2, 1.
Clicker Questions
import statement
• import pulls a module in to your program.• A module is a file with code and variables in it.– math module has sin(), cos(), round(), pi, e, etc.– myro has init(), forward(), backward(), etc.
• import loads the module in, but all the stuff in it is still in it. Access it via the “dot operator”.– import loads the “box” in but your code still has to
reach into the box to get at the functions, variables, etc.• e.g., math.sin(), math.pi
import (cont)
• If you want to pull something (everything) out of the “box”, you can do this from math import *from math import sin
• Then you don’t need to tell your code to reach into the module to get the function/variable.– e.g., can use sin() instead of math.sin() – init() instead of myro.init().
Assignments
• Do the few TuringsCraft questions before lab on Thursday.