Karel 4

Calvin (Deutschbein)

W2D2: 4 Sep

Announcements

• Starting this week... sections!
  • Check email from jjrembold@
  • Subject: Info on your CS 151 small section time and leader!
    • 1 hour sometime on W or Th
    • Mandatory: Each missed section is 5% off final grade (more or less)
    • Help us help you - if you have a conflict, get sick, etc. - reach out jjrembold@
• By MONDAY 11:59 PM: "Problem Set 1: Karel" assignment.
  • One problem (probably) using "def" and "for"
  • One problem using at least "while" and maybe the other three.

Today

• Running Karel review.
  • Github classroom.
  • Extracting Zip files.
  • Running Karel.
• "Control Flow" again.
  • The "def" (for "define") keyword and functions
  • The "for" keyword and loops
  • The "if" keyword and conditionals
  • The "while" keyword and conditional loops

Course Webpage

• From the course webpage...
• Select "Problem Set 1: Karel"

Problem Set 1: Karel

• From "Problem Set 1: Karel"...
• Select the hyperlink to Github Classroom.
  • It will be labeled as "Github Classroom Link"
  • It will be of the form "https://classroom.github.com" and some trailing letters and numbers.

Github Classroom: Pre-Accept

• From the link to Github Classroom.
• Select Accept this assignment.
  • You will have to wait a moment.

Github Classroom: Post-Accept

• From Accept this assignment...
• Select the link to the assignment repository.
  • It will be labeled as "Your assignment repository has been created."
  • It will be of the form "https://github.com/<your @>/problem-set-1-karel-<your @>

Assignment Repository

• From the assignment repository....
• Select <> Code ▼

Download ZIP

• From <> Code ▼...
• Select "Download ZIP"
  • Your browser will begin downloading a file.

Browser Downloads

• From the browser pop-up for downloading a file...
• Select "problem-set-1-karel-<your @>-main"
  • A new window will open with the ZIP file

ZIP File Window

• From the ZIP file window...
• Select "Extract: Compressed Folder Tools"

I believe on Mac you can simply doubleclick.

Compressed Folder Tools

• From the "Compressed Folder Tools"
• Select "Extract all"
  • A menu will open

Extract Menu

• From the new menu (called "Select a Destination and Extract Files")
• Select "Extract"
  • A new window will open with a folder (not a ZIP file) called "problem-set-1-karel-<your @>-main"

Folder Window

• From the new folder window
• Select "problem-set-1-karel-<your @>-main"
• A new window will open with a folder (not a ZIP file) called "problem-set-1-karel-<your @>-main"

Files Window

• From "problem-set-1-karel-<your @>-main" folder
• Right-click "Karel_Newspaper.py"
  • Find a way to run "Karel_Newspaper.py", such via Python, in IDLE, or in VS Code
  • Find a way to edit "Karel_Newspaper.py", such as via Notepad++, BBEdit, or in VS Code

How I Code 1

• I leave open the folder to double-click "Karel_Newspaper.py" to test my code.
• I open "Karel_Newspaper.py" in Notepad++ to edit my code.
  • Before doing anything else, I add a move() command to every function, just to make sure Karel moves at all.
  • This is before I double-click:

How I Code 2

• This is after I double-click:

How I Code 3

• This is after I click the "play" button (Karel moves once for the single move in main):

How I Code 4

• I relaunch Karel every time I run (Karel seems very buggy to me)
• I sometimes leave Karel open while writing code to look at the world.
• As a rule, I do not write/change more than one line of code without testing.

How I Submit 1

• When I am done, I "submit" the homework via Github classroom.

How I Submit 2

• In Github classroom I double-click the relevant Python (.py) file
  • In this case "Karel_Newspaper.py"

How I Submit 3

• From the relevant Python (.py) file's page on Github, select the (very tiny) edit button, donated with an icon that may look like a pen or pencil.

How I Submit 4

• This opens the Github online editor:

How I Submit 5

• Select all text in the Github online editor (via ctrl+a or cmd+a)

How I Submit 6

• Delete all text in the Github online editor (via Backspace "←" or Delete "DEL" )

How I Submit 7

• Select all text in Notepad++ or equivalent (via ctrl+a or cmd+a)

How I Submit 8

• Copy (ctrl/cmd+c) in Notepad++ and Paste (ctrl/cmd+c) in Github, or...
• Drag and drop:

How I Submit 9

• Select Commit changes...

Submitted!

• Select Commit changes (with no "...")
  • When you press that button, the work is "turned in"
  • You may update it any time until the due date!

How do I know?

• You can make sure the homework is submitted by downloading the zip file again and making sure your code runs the way you expect!
• I would do this until you feel confident or just to set your mind at ease!
• You may update it any time until the due date!
• You can see here it says it is updated:

Today

• ✓ Running Karel review.
  • ✓ Github classroom.
  • ✓ Extracting Zip files.
  • ✓ Running Karel.
• "Control Flow" again.
  • The "def" (for "define") keyword and functions
  • The "for" keyword and loops
  • The "if" keyword and conditionals
  • The "while" keyword and conditional loops

Control Flow

		Does it happen more than once?
		No	Yes (it's a loop)
Is it conditional (do we ask Karel a question)?	No	'def' functions Define a series of actions We can "call" functions Code in 'def' doesn't run unless called	'for' loop Code in the loop runs i times Good for repeated actions
	Yes	'if' statement Code in the statement runs if Karel answers "yes" to some question Good if what you want to do depends on walls/beepers/etc	'while' loop Code in the statement runs as long as Karel answers "yes" to some question Good for completing tasks that require repeated actions.

naskarel

• Imagine Karel on a 10x10 grid.
• Karel wants to pretend to be a NASCAR and race around the outside.
• The outside is always ten spaces long.
• We could do this: import karel def main(): move() move() move() move() move() move() move() move() move() turn_left() # can only turn left move() # move to end move() move() move() move() move() move() move() move() turn_left() # can only turn left move() # move to end move() move() move() move() move() move() move() move() turn_left() # can only turn left move() # move to end move() move() move() move() move() move() move() move() turn_left()

naskarel: def

• Imagine Karel on a 10x10 grid.
• Karel wants to pretend to be a NASCAR and race around the outside.
• The outside is always ten spaces long.
• Or we could use define (at the bottom) and call (within main) "move_nine"

  import karel def main(): move() # move to end move() move() move() move() move() move() move() move() turn_left() move() # move to end move() move() move() move() move() move() move() move() turn_left() move() # move to end move() move() move() move() move() move() move() move() turn_left() move() # move to end move() move() move() move() move() move() move() move() turn_left()

  import karel def main(): move_nine() turn_left() move_nine() turn_left() move_nine() turn_left() move_nine() turn_left() def move_nine(): move() # 1 move() # 2 move() # 3 move() # 4 move() # 5 move() # 6 move() # 7 move() # 8 move() # 9

Which is easier?

Anatomy of a def

Which is easier?

naskarel: for

• Imagine Karel on a 10x10 grid.
• Karel wants to pretend to be a NASCAR and race around the outside.
• The outside is always ten spaces long.
• We could for loops to move across all ten spaces.

  import karel def main(): move() # move to end move() move() move() move() move() move() move() move() turn_left() move() # move to end move() move() move() move() move() move() move() move() turn_left() move() # move to end move() move() move() move() move() move() move() move() turn_left() move() # move to end move() move() move() move() move() move() move() move() turn_left()

  import karel def main(): for i in range(9): move() turn_left() for i in range(9): move() turn_left() for i in range(9): move() turn_left() for i in range(9): move() turn_left()

Which is easier?

naskarel: double or nothing

• Imagine Karel on a 10x10 grid.
• Karel wants to pretend to be a NASCAR and race around the outside.
• The outside is always ten spaces long.
• We use a for loop in a function to make nicer code...

  import karel def main(): move() # move to end move() move() move() move() move() move() move() move() turn_left() move() # move to end move() move() move() move() move() move() move() move() turn_left() move() # move to end move() move() move() move() move() move() move() move() turn_left() move() # move to end move() move() move() move() move() move() move() move() turn_left()

  import karel def main(): move_nine() turn_left() move_nine() turn_left() move_nine() turn_left() move_nine() turn_left() def move_nine(): for i in range(9): move()

Which is easier?

naskarel: double or nothing

• Imagine Karel on a 10x10 grid.
• Karel wants to pretend to be a NASCAR and race around the outside.
• The outside is always ten spaces long.
• This makes it easier to see we can loop in main as well!

  import karel def main(): move_nine() turn_left() move_nine() turn_left() move_nine() turn_left() move_nine() turn_left() def move_nine(): for i in range(9): move()

  import karel def main(): for i in range(4): move_nine() turn_left() def move_nine(): for i in range(9): move()

Which is easier?

naskarel: 40 vs 7 lines

Today

• ✓ Running Karel review.
  • ✓ Github classroom.
  • ✓ Extracting Zip files.
  • ✓ Running Karel.
• "Control Flow" again.
  • ✓The "def" (for "define") keyword and functions
  • ✓The "for" keyword and loops
  • The "if" keyword and conditionals
  • The "while" keyword and conditional loops

Unlost

• Imagine Karel_Newspaper but with variable houses.

What if this were 2x2?
(I was talking to my elders about home-ownership this weekend 😭)

unlost

We could: Drop a beeper Cling to the left wall until we find a beeper. Pick it up and turn around. Cling to the right wall until we find a beeper.

Not necessarily easier, but more general.

On the homework, you can't drop a beeper (you have none) - I'm not doing the problem for you.

unlost

import karel def main(): put_beeper() cling_left_until_beeper() pick_and_rev() cling_right_until_beeper() pick_beeper() def cling_left_until_beeper(): move() def pick_and_rev(): move() def cling_right_until_beeper(): move()

unlost

import karel def main(): put_beeper() cling_left_until_beeper() pick_and_rev() cling_right_until_beeper() pick_beeper() def cling_left_until_beeper(): # this will hit walls while no_beepers_present(): move() def pick_and_rev(): move() def cling_right_until_beeper(): move()

unlost

import karel def main(): put_beeper() cling_left_until_beeper() pick_and_rev() cling_right_until_beeper() pick_beeper() def cling_left_until_beeper(): while no_beepers_present(): if front_is_blocked(): # avoid walls turn_right() # or 3 left move() def pick_and_rev(): move() def cling_right_until_beeper(): move()

unlost

import karel def main(): put_beeper() cling_left_until_beeper() pick_and_rev() cling_right_until_beeper() pick_beeper() def cling_left_until_beeper(): while no_beepers_present(): if front_is_blocked(): # avoid walls turn_right() # or 3 left if left_is_clear(): # 'cling' left turn_left() move() def pick_and_rev(): move() def cling_right_until_beeper(): move()

unlost

• Like this:
  

unlost

• Try it: def main(): while no_beepers_present(): if front_is_blocked(): # avoid walls turn_left() turn_left() turn_left() # or 3 left if left_is_clear(): # 'cling' left turn_left() move()

Exercise

• Do "Problem Set 1: Karel"
  • Use comments
  • The first problem "newspaper" benefits from functions, and perhaps for loops
    • It is possible, but annoying, to do without either
  • The second problem, "painting" benefits from 'while' loops (and could use 'if')
    • I used four (4) 'while' loops, and no 'if' statements or 'for' loops

Announcements

• Starting this week... sections!
  • 1 hour sometime on W or Th
  • Mandatory: Each missed section is 5% off final grade (more or less)
  • Help us help you - if you have a conflict, get sick, etc. - reach out ASAP.
• By MONDAY 11:59 PM: "Problem Set 1: Karel" assignment.
  • One problem (probably) using "def" and "for"
  • One problem using at least "while" and maybe the other three.