Compsc psci 101 101 Turtle, B Bagels, s, L Loop T p Tracing - - PowerPoint PPT Presentation

Compsc psci 101 101 Turtle, B Bagels, s, L Loop T p Tracing ng, F Files Liv ive L Lec ecture

9/15/2020 Compsci 101, Fall 2020 1

Susan Rodger September 15, 2020

Announcements

• APT

APT-2 du due toni night!

• Remember you get 24-hour grace period, can’t

turn in after that!

• APT

APT-3 ou

• ut tod
• day – due 9

9/22 22

• Assignment 2

t 2 Turtl tles o

• ut

t – due due 9 9/29

• Lab 4

b 4 Friday – has pr prelab t to do do be before l lab! b!

9/15/2020 Compsci 101, Fall 2020 2

Exam 1 Studying

• Exam

am 1 1 is Sep Sept 24, 24, nex ext Th Thursday

• Cove

vers top

• pics

cs th through th this is w week

• Not while loops, not files
• How
• w to

to stu tudy

• Write code on paper or type code in a plain text file
• Redo code you have already done, we did class
• Try things in Python Tutor, in Python Console
• Review all notes
• Old tests on Resources tab
• Spring 18 on, is Python 3, Before that Python 2
• Try timing yourself on old exams?
• CS101 Reviewer APP – use in prelab for Lab 4

9/15/2020 Compsci 101, Fall 2020 3

APT Quiz 1

• APT Quiz 1

1 is 9/ 9/25 25-9/28 28 ( (no l lab o

• n 9

9/25) 5)

• Open

en around und 8 8am 9 9/25

• Pic

ick y your r start t tim ime,

• Once you start, You have 2.5 hours
• If you get accommodations, you get those
• 3 APTs t

to

• sol
• lve
• Will put

ut up up p problems f from a an n old APT APT Q Qui uiz s so y you u can an p prac actice

9/15/2020 Compsci 101, Fall 2020 4

WOTO-1 – Turtles Simple http://bit.ly/101f20-0915-1

• If you a

are d e done e early, revi vise a e and c d collab aborate e on your n note tes!

• In y

your g groups ps:

• Come to a consensus

9/15/2020 Compsci 101, Fall 2020 5

WOTO-2: Let’s draw a triangle! http://bit.ly/101f20-0915-2

• Equila

lateral t l triangle le

• Corner degrees: 60
• Side length: 100

9/15/2020 Compsci 101, Fall 2020 6

WOTO-2: Let’s draw a triangle! http://bit.ly/101f20-0915-2

• Equila

lateral t l triangle le

• Corner degrees: 60
• Side length: 100

9/15/2020 Compsci 101, Fall 2020 7

WOTO-2: Let’s draw it 3 times!

• TPS: W

What will t will the t turtle d dra raw?

• Note: Think about where the turtle is and facing

after each iteration

9/15/2020 Compsci 101, Fall 2020 8

Option 1 (Draw 3 triangles on top of each

• ther)

Option 2 Option 3 Option 4

Orientation and location matters!

Bagels (Accumulation)

9/15/2020 Compsci 101, Fall 2020 9

This Photo by Unknown Author is licensed under CC BY-NC-ND

APT Bagels

• How figure

e out h how many b y bag agel els n need eeded? d?

• 7-steps!

9/15/2020 Compsci 101, Fall 2020 10

9/15/2020 Compsci 101, Fall 2020 11

Examples

9/15/2020 Compsci 101, Fall 2020 12

Step 1 and 2

• Step

ep 1 1: S Solve e an i instan ance (t (think)

• orders = [11, 3, 24, 17]

9/15/2020 Compsci 101, Fall 2020 13

Step 1 and 2

• Step

ep 1 1: S Solve e an i instan ance ( (TPS)

• orders = [11, 3, 24, 17]
• Total: 58
• Step 2

2: W What di did w d we do do?

• 11 + 3 + (24+2) + (17+1) = 58

9/15/2020 Compsci 101, Fall 2020 14

WOTO-3 Step 3: Generalize http://bit.ly/101f20-0915-3

9/15/2020 Compsci 101, Fall 2020 15

WOTO-3 Step 3: Generalize

• Go t

throug ugh l h list

• If

f less th than 12 12

• Do nothing
• If grea

eater er t than an o

• r equal

al t to 12

• Add however many times 12 goes into the order
• Sum e

everything

9/15/2020 Compsci 101, Fall 2020 16

Step 4: Test steps

• Go through list
• If less than 12
• Do nothing
• If greater than or equal

to 12

• Add however many times

12 goes into the order

• Sum everything
• [11, 22, 33, 44, 55]
• 11
• Nothing (less than 12)
• 22
• +1
• 33
• +2
• 44
• +3
• 55
• +4
• Sum: 175

9/15/2020 Compsci 101, Fall 2020 17

Step 5: Code

• Go through list
• If less than 12
• Do nothing
• If greater than or equal

to 12

• Add however many

times 12 goes into the

• rder
• Sum everything
• for loop!
• if statement
• TPS: if’s or if…else

statement?

• floor div: //

9/15/2020 Compsci 101, Fall 2020 18

Could we use the accumulator pattern? Yes!

Step 5: Code

9/15/2020 Compsci 101, Fall 2020 19

Initialize before loop Update inside loop Do something with value after loop

Donald Knuth

• Until recently …
• Was "The Donald"
• Turing, Hopper, more …
• Author of many works

Art of Computer Programming Mad Magazine when 19 (author of TeX) “I can’t go to a restaurant and order food because I keep looking at the fonts on the menu.”

9/15/2020 Compsci 101, Fall 2020 20

Code-Tracing a Loop

1.

• 1. Find

d the c e chan anging va variab ables es/expressions 2.

• 2. Crea

eate t table, columns a are va e variab ables/ex expres essions

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

3.

• 3. Each r

row is w is an it iteratio ion o

• f the lo

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

9/17/2020 Compsci 101, Fall 2020 21

WOTO Loop Tracing http://bit.ly/101f20-0915-4

• Remem

ember t the e steps eps ( (1) F Find t the e chan anging va variab able/expressions, ( (2) C Crea eate t the t e tab able w e with thes ese as as t the e column, and ( (3) E Eac ach row is a an ite terati tion

• n o
• f the loop
• In y

your g groups ps:

• Come to a consensus

9/17/2020 Compsci 101, Fall 2020 22