Compsci 101 101 Turtle, B , Bag agel els, L , Loop T op - - PowerPoint PPT Presentation

Compsci 101 101 Turtle, B , Bag agel els, L , Loop T

• p Tracing, Files

es Par art 1 1 of

• f 4

9/15/2020 Compsci 101, Fall 2020 1

Susan Rodger September 15, 2020

I is for …

• Identity
• Who are you? Computer Science Student
• Invariant
• Reasoning formally and informally about loops
• Internet
• Network of networks
• Far more than that!

9/15/2020 Compsci 101, Fall 2020 2

PFTD

• Turtle

le

• Bag

agels ls A APT

• Trace t

ace throug ugh h loops

• File

iles

9/15/2020 Compsci 101, Fall 2020 3

Run Turtle, Run

9/15/2020 Compsci 101, Fall 2020 4

Turtle Programming

• Must

st:

• Import turtle module
• Create window/Screen
• Last thing - exit on click
• Create turtles to use, name/type/value
• Revi

view T Turtle c commands a and concepts

• http://bit.ly/turtle_tutorial for more, and book
• Se

See Snowpeo wpeopl ple.py, , ColorMyWorl rld.p d.py, a and Sp Spiro.py for so some i ideas

• Color, Position, Leaving Turtle where started
• Many more commands than this

9/15/2020 Compsci 101, Fall 2020 5

Put yourself in the turtle t…

t.fo forward rd(50) 50) # # turtle le moves forward # # drawing a line a line t.left(90) # # tu turtl tle tu turns s to to its s left t.penc encolo lor(“blue”) # c # cha hange pen en colo lor t.fo forward rd(10 100) 0) # # turtle le moves es forward # # drawing lin line, ne new c colo lor

9/15/2020 Compsci 101, Fall 2020 6

Example: simple.py

9/15/2020 Compsci 101, Fall 2020 7

Example: Simple.py parts

• Im

Impor

• rt a

at t the t top

• p
• Create c

canv nvas

• Create t

turtle le

• Call f

ll funct ctio ion t n to draw

• Clo

lose c can anvas w when hen cli lick o

• n

n it it

9/15/2020 Compsci 101, Fall 2020 8

Example: Simple.py parts

• Im

Impor

• rt a

at t the t top

• p
• Create w

window

• Create t

turtle le

• Call f

ll funct ctio ion t n to draw

• Clo

lose c can anvas w when hen cli lick o

• n

n it it

9/15/2020 Compsci 101, Fall 2020 9

Example: Simple.py parts

• Im

Impor

• rt a

at t the t top

• p
• Create c

canv nvas

• Create t

turtle le

• Call f

ll funct ctio ion t n to draw

• Clo

lose c can anvas w when hen cli lick o

• n

n it it

9/15/2020 Compsci 101, Fall 2020 10

Example: Simple.py parts

• Im

Impor

• rt a

at t the t top

• p
• Create c

canv nvas

• Create t

turtle le

• Call f

ll funct ctio ion t n to draw

• Clo

lose c can anvas w when hen cli lick o

• n

n it it

9/15/2020 Compsci 101, Fall 2020 11

Example: Simple.py parts

• Im

Impor

• rt a

at t the t top

• p
• Create c

canv nvas

• Create t

turtle le

• Call f

ll funct ctio ion t n to draw

• Clo

lose c can anvas w when hen cli lick o

• n

n it it

9/15/2020 Compsci 101, Fall 2020 12

Example: Simple.py DrawPicture

9/15/2020 Compsci 101, Fall 2020 13

Example: Simple.py DrawPicture

9/15/2020 Compsci 101, Fall 2020 14

Example: Simple.py DrawPicture

9/15/2020 Compsci 101, Fall 2020 15

Example: Simple.py DrawPicture

9/15/2020 Compsci 101, Fall 2020 16

Example: Simple.py DrawPicture

9/15/2020 Compsci 101, Fall 2020 17

Compsci 101 101 Turtle, B , Bag agel els, L , Loop T

• p Tracing, Files

es Par art 2 2 of

• f 4

9/15/2020 Compsci 101, Fall 2020 18

Susan Rodger September 15, 2020

What are key concepts in Spiro.py?

9/15/2020 Compsci 101, Fall 2020 19

Create screen/window Close on click Create turtle 1 – slowest 10 – fastest 0 – No animation Import turtle

Useful turtle functions

• forward(n)/backward(n) – move t

turtle le n n pixels els

• left(n)/right(n) – turn t

n turtle n le n degree ees

• pendown()/pendup() – whethe

her a act ctuall ually d drawing ing

• setposition(x, y) – puts tu

ts turtl tle i in this ( s (x,y ,y) ) coordina inate ( (a.k .k.a .a. . goto, , setpos)

• sethead(n) – poin

ints t tur urtle in in this his dir irection ( (n= n=0 is 0 is east) t)

• Many

ny more i in document entatio ion! n!

• https://docs.python.org/3/library/turtle.html

9/15/2020 Compsci 101, Fall 2020 20

ColorMyWorld.py

9/15/2020 Compsci 101, Fall 2020 21

Turtle Concepts

• Create

e a screen s een so you c u can an ..

• Exit On Click
• Some other Screen Functions
• Create

e a turtle s e so you c u can … n …

• Move and draw using the turtle
• Drawing C

ng Concepts

• Pen [up and down]
• Fill
• Color
• Position

9/15/2020 Compsci 101, Fall 2020 22

Compsci 101 101 Turtle, B , Bag agel els, L , Loop T

• p Tracing, Files

es Par art 3 3 of

• f 4

9/15/2020 Compsci 101, Fall 2020 23

Susan Rodger September 15, 2020

Code-Tracing a Loop

1.

• 1. Find the c

chang anging ing v variab iable les/expres essio ions ns 2.

• 2. Create table

le, c colum lumns ns a are v varia iable les/e /expressio ions ns

• 1. First column is loop variable
• 2. Add columns to help track everything else

3.

• 3. Eac

ach row is is an it an iter eration o

• f the lo

he loop

• 1. Before execute code block, copy down each

variable’s value

• 2. Execute code block, update a value in the row

as it changes

9/15/2020 Compsci 101, Fall 2020 24

Code-Tracing a Loop

1.

• 1. Find the c

chang anging ing v variab iable les/expres essio ions ns 2.

• 2. Create table

le, c colum lumns ns a are v varia iable les/e /expressio ions ns

• 1. First column is loop variable
• 2. Add columns to help track everything else

9/15/2020 Compsci 101, Fall 2020 25

What should be the table’s columns?

Code-Tracing a Loop

1.

• 1. Find the c

chang anging ing v variab iable les 2.

• 2. Create table

le, c colum lumns ns a are t the va varia iables les

• 1. First column is loop variable
• 2. Add columns to help track everything else

9/15/2020 Compsci 101, Fall 2020 26

Loop variable Other variable Useful expression to track

Fill in table

9/15/2020 Compsci 101, Fall 2020 27

1.

• 1. Bef

efore e e execut cute c e code e bl block, c copy do down wn eac each v var ariable le’s v val alue 2.

• 2. Execut

ecute c e code b e block ck, , up update a a val alue in in the he row as as it c chang anges

i idxMax lst[idxMax] lst[i] lst[idxMax] < lst[i]

mystery([2, 12, 4, 15, 15])

Fill in table

9/15/2020 Compsci 101, Fall 2020 28

1.

• 1. Bef

efore e e execut cute c e code e bl block, c copy do down wn eac each v var ariable le’s v val alue 2.

• 2. Execut

ecute c e code b e block ck, , up update a a val alue in in the he row as as it c chang anges

i idxMax lst[idxMax] lst[i] lst[idxMax] < lst[i] 2 2 False 1

mystery([2, 12, 4, 15, 15]) #1

Fill in table

9/15/2020 Compsci 101, Fall 2020 29

1.

• 1. Bef

efore e e execut cute c e code e bl block, c copy do down wn eac each v var ariable le’s v val alue 2.

• 2. Execut

ecute c e code b e block ck, , up update a a val alue in in the he row as as it c chang anges

i idxMax lst[idxMax] lst[i] lst[idxMax] < lst[i] 2 2 False 1 0 1 2 12 True

mystery([2, 12, 4, 15, 15]) #2

Compsci 101 101 Turtle, B , Bag agel els, L , Loop T

• p Tracing, Files

es Par art 4 4 of

• f 4

9/15/2020 Compsci 101, Fall 2020 30

Susan Rodger September 15, 2020

Examples of Processing Data

• Lec

ecture 1: 1: coun unt le letters in in Bib ible le

• Anothe

her e example le: G Google le Ngra gram viewe wer

• https://books.google.com/ngrams

9/15/2020 Compsci 101, Fall 2020 31

Studying Language Evolution

• Ngra

gram info forms rms h how word rds e evolve

• From dove t

to dived

• https://www.youtube.com/watch?v=tFW7orQsBuo

9/15/2020 Compsci 101, Fall 2020 32

Sequences, Repetition

• Par

arameters? W Wha hat ar are t the hey t to this his quer uery?

• https://books.google.com/ngrams/graph?conte

nt=terrorism%2Cpatriot&year_start=1800&year _end=2000&corpus=15&smoothing=3

9/15/2020 Compsci 101, Fall 2020 33

What can the URL tell you?

Sequences, Repetition

• Par

arameters? W Wha hat ar are t the hey t to this his quer uery?

• https://books.google.com/ngrams/graph?conte

nt=terrorism%2Cpatriot&year_start=1800&year _end=2000&corpus=15&smoothing=3

9/15/2020 Compsci 101, Fall 2020 34

Search words Year start search Year end search

Processing Data

• How do we f

e find ind the he lo long ngest word in .. in .. Any ny t tex ext?

• How do we

e find ind t the he w word t tha hat o

• ccurs t

the he m most?

• How is t

this r rela lated ed t to how Google S le Search w h works?

• Tex

ext f file iles c can an b be e vie iewed as seq equences

• Sequences of lines
• Each line is a string
• Some clean-up because of ‘\n’

9/15/2020 Compsci 101, Fall 2020 35

File Pattern: One line at a time

• Simples

lest a and reasona nably ef efficie icient nt Python n pat attern

• Open, loop, close, return/process
• LineCounter.py in code zip file
• File a

e as s seque uenc nce

• One line at-a-time
• As

Asymmetry i in Open v n vs Close s e step eps

9/15/2020 Compsci 101, Fall 2020 36

altCount.py

• a

9/15/2020 Compsci 101, Fall 2020 37

File Objects

• A file

ile is is an an objec ect, lik like a a string

• Functions applied to object: len(“word”)
• To get file object use open(“data.txt”)
• What is returned? Integer value, file object
• Often

n met etho hods ( (aka f funct ctio ion) n) a applied ied t to object ct

• f.readlines(), f.read(), f.close()
• Just like: st.lower(), st.count(“e”)

9/15/2020 Compsci 101, Fall 2020 38

Text File Processing Pattern

• See m

modul ule e FileStuff.py in in c code zip ip f file ile

• If newline ’\n’ is read, call .strip()
• If want to break line into “words”, call .split()
• Proces

cess the l e list r ret etur urne ned b by .split()

• May need to convert strings to int or float or …
• The

he for line in f: pat atter ern i is ef effici cien ent

• Contrast list returned by f.readlines()

9/15/2020 Compsci 101, Fall 2020 39

FileStuff.py: avgWord

• a

9/15/2020 Compsci 101, Fall 2020 40