Turtle Graphics Victor Norman CS104 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 in : # 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 Examples for val in [0, 1, 2, 3, 4, 5]: turt.forward(50) turt.left(60) total = 0 for val in [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]: total = total + val print(total) total = 0 for val in range(1, 21): total = total + val print(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.