Course Information

Section 2: MWF 10:30–11:20, Sci 256
Professor: Sara Mathieson
Office: Sci 249
Office hours: Fridays, 3-5pm
Lab Instructor: Sara "Scout" Sinclair
Office: Sci 262A
Office hours: Mondays, 2-3:30 and Thursdays, 10:30-11:30

Piazza: CS21 Q&A forum

Links to all sections:

• Aline Normoyle (MWF 9:30–10:20)
• Sara Mathieson (MWF 10:30–11:20)
• Sara Mathieson (MWF 11:30–12:20)

Welcome to CS21. This course will introduce fundamental ideas in computer science while also teaching you how to write computer programs. We will study algorithms for solving problems and implement solutions in the Python programming language. Python is an interpreted language that is known for its ease of use. We also introduce object-oriented programming and data structures. A deeper coverage of these topics will be presented in CS 35.

This course is appropriate for all students who want to learn how to write computer programs and think like computer scientists. It is the usual first course for computer science majors and minors. Students with advanced placement credit or extensive programming experience should place out of this course and instead begin with CS31 or CS35.

Textbook:

We will primarily be using the online book How to think like a computer scientist: Learning with Python by Elkner, Downey and Meyers.

See the Schedule for each week's reading assignment.

Here are a few other useful online resources:

• Basic Unix Commands
• atom basics
• Python Tutor
• The Python tutorial
• Python documentation (Note: we are using v3.6)

Goals for the course:

By the end of the course, we hope that you will have developed the following skills:

• Given a program, be able to simulate on paper how a computer would execute the program, and show the results that would be produced.
• Given a problem, be able to design a clear, concise, and correct pseudocode algorithm to solve it.
• Given a pseudocode algorithm, be able to successfully implement it in Python.
• Be able to use top-down design to sub-divide a large problem into reasonably-sized modular sub-problems.
• Given several algorithms for solving the same problem, be able to analyze which algorithm would be more efficient in terms of running time.
• Develop debugging and unit testing skills. Consistently use these skills while implementing programs.

Schedule

Here is the tentative schedule; it may change as we go...

WEEK	DAY	ANNOUNCEMENTS	TOPIC & READING	LABS
1	Sep 03		Course Introduction algorithms, problem solving python, unix, atom editor writing and running a program using def main(): data types for numbers (int, float) and text (str) variables, assignment simple arithmetic displaying text: print() user input: input() Ch 1: The way of the program Ch 2: Variables, expressions and statements Ch 4, Sec 9: keyboard input Ch 4, Sec 10: type conversion	Mon: Slides 1 Handout 1 Wed: Slides 2 Transcript 2 welcome.py Fri: Slides 3 Transcript 3 welcome.py Lab 0: Unix, Editing Lab Notes
	Sep 05
	Sep 07
2	Sep 10		Numbers, Strings, and Loops more arithmetic using libraries: from math import * string manipulation repetition: for loops, sequences, range() accumulator pattern list data type: indexing, len() Ch 2: Variables, expressions and statements Ch 2: lists, looping, range() Ch 7: Strings (sections 1-3, 5-6 only)	Mon: Slides 4 Transcript 4 graduate.py right_triangle.py Wed: Slides 5 Transcript 5 xo.py square.py Fri: Slides 6 Transcript 6 blastoff.py sum_loop.py Lab 1: First Programs
	Sep 12
	Sep 14	Drop/add ends
3	Sep 17		Conditions and Boolean Logic advanced for loops boolean type relational operators (<, >, ==, !=, etc) logical operators (and, or, not) branching if/elif/else nesting string comparisons, ASCII string/print formatting Ch 4: Conditionals (skip sections 8,11) Ch 7: Strings (in operator) Ch 7: Strings (str formatting)	Mon: Slides 7 Transcript 7 rand_loop.py stretch.py username.py Wed: Slides 8 Transcript 8 conditionals1.py Fri: Slides 9 lettercount.py movie.py Lab 2: Numbers and Strings Lab Notes
	Sep 19	Q1 study guide
	Sep 21	Quiz 1
4	Sep 24		First Functions, while Loops while loops writing simple functions arguments, parameters, return values stack diagrams Ch 3: Functions (just 3.1 - 3.3) Ch 5: Fruitful functions (just 5.1, 5.2) Ch 6: Iteration	Mon: Slides 10 class_functions.py factorial.py Wed: Slides 11 mystery_errors.py first_last.py Fri: Slides 12 while_5.py while_s.py while_die.py Lab 3: If/Else
	Sep 26
	Sep 28
5	Oct 01		Fruitful Functions list data type indexing, slicing, and iteration of lists mutability of lists more practice with functions boolean functions passing lists to functions more stack diagrams Ch 3: Functions Ch 5: Fruitful functions Stack diagrams handout A Better/Longer Stack Diagram Example Another Stack Diagram Example Ch 9: Lists (sections 1-3, 5, 6, 8) Ch 7.4: String Slicing	Mon: Slides 13 Transcript 13 build_list.py Wed: Slides 14 Transcript 14 shuffle_list.py Handout 2 Fri: Slides 15 Handout 3 Lab 4: While loops/Functions
	Oct 03	Q2 study guide
	Oct 05	Quiz 2
6	Oct 08		Graphics, Using Objects object-oriented programming create objects and call methods getter and setter methods dot notation intro to graphics OOP using the graphics library RGB colors animation Ch 8: Graphics Case Study Notes on the Zelle graphics library Zelle's Chapter 5: Objects and graphics Zelle Graphics Module	Mon: Slides 16 Transcript 16 circles.py Wed: Slides 17 box.py Fri: Slides 18 text_move.py nested_loop.py Lab 5: More Functions Lab Notes
	Oct 10
	Oct 12
	Oct 15	Fall Break
	Oct 17
	Oct 19
7	Oct 22		Top-Down Design top-down design bottom-up implementation incremental testing and development prototyping functions list-of-lists random library reading files Ch 10, Sec 8: Text Files Intro and CompSci sections from Wikipedia TDD Ch 10, Sec 6: str, list methods	Mon: Slides 19 Handout 4 colleges_file.py Wed: Slides 20 Transcript 20 Handout 5 word_guessTDD.py Fri: Slides 21 Handout 6 word_guesser.py Lab 6: Graphics
	Oct 24
	Oct 26
8	Oct 29			Mon: Slides 22 Handout 7 9letters_tdd.py 9letters_file.py Wed: Slides 23 ninja_hours.py Max Pumpkin Fri: Slides 24 pumpkin_tdd.py Mon: Slides 25 linear_search.py Wed: Slides 26 Handout 8 Fri: Slides 27 binary_search.py searches.py dictionary_tests.py Lab 7: Top-Down Design
	Oct 31	Q3 study guide
	Nov 02	Quiz 3
9	Nov 05		Searching linear search analysis of algorithms big-O notation binary search nested loops Binary Search (skip the recursive version) Ben's musicAlgo videos
	Nov 07
	Nov 09	CR/NC/W Deadline
10	Nov 12		Sorting selection sort bubble sort analysis of algorithms other sorting algorithms Ben's musicAlgo selection sort video interactivepython selection sort interactivepython bubble sort	Mon: Slides 28 Handout 9 Wed: Slides 29 sorts_pseudocode.py sorts.py Fri: Slides 30 sort_runtime.py Lab 8: Searching
	Nov 14	Q4 study guide
	Nov 16	Quiz 4
11	Nov 19		Classes and Objects object-oriented programming revisited creating our own classes instance variables (objects) of classes member variables and methods constructor: __init()__ getters/setters interfaces and implementations Ch 13: Classes and objects Ch 14: Classes and functions Ch 15: Classes and methods	Mon: Slides 31 pie.py Transcript 31 Wed: Slides 32 die.py student.py snowflake.py Lab 9: Sorting
	Nov 21
	Nov 23	Thanksgiving
12	Nov 26		Classes and Objects more examples of classes Ch 13: Classes and objects Ch 14: Classes and functions Ch 15: Classes and methods	Mon: Slides 33 snowflake.py snow_main.py screen_saver.py Wed: Slides 34 screen_saver.py Fri: Slides 35 baseball.py player.py team.py Lab 10: Classes
	Nov 28	Q5 study guide
	Nov 30	Quiz 5
13	Dec 03		Recursion recursive call base case designing recursive solutions stack diagrams recursion on lists, numbers, and strings recursive binary search Recursion (from Wikipedia) PYTHON TUTOR	Mon: Slides 36 Transcript 36 factorial.py Wed: Slides 37 fibonacci.py recursive_circles.py Fri: Slides 38 fractal_tree.py Lab 11: Recursion
	Dec 05
	Dec 07
14	Dec 10	Final study guide	Wrap up	Mon: Slides 39 badpassword.py
	Dec 15	Final Exam: Sat, Dec 15, 2-5pm, Sci Cen 101

Grading Policies

Grades will be weighted as follows:

35%	Lab assignments
30%	Quizzes
30%	Final Exam
5%	Class Participation

Exam and Quizzes

Quizzes will be given at the beginning of class on the days posted on the Schedule. Please look over these dates carefully and contact the professor in advance if you cannot be in class for a quiz.

If you are not present on the day of a quiz, and do not let me know ahead of time that you are missing class, you will receive a zero for that quiz.

There will be one final exam for the semester. Details and dates will be released during the semester. Please read the section on accommodations if you are in need of extra time. You must inform me of accommodations or conflicts at least 2 weeks in advance of the exam.

Lab Policy

This course features weekly lab assignments which are the largest component of your course grade. Lab attendance is required by all students, unless you have already completed and submitted the lab assignment for the week. You must attend the lab session for which you are enrolled:

Weekly Lab Sessions
CS21 A 1:15—2:45pm Tuesdays	Sara Mathieson	Sci 240
CS21 B 3:00—4:30pm Tuesdays	Scout Sinclair	Sci 240
CS21 C 1:15—2:45pm Wednesdays	Aline Normoyle	Sci 240
CS21 D 3:00—4:30pm Wednesdays	Aline Normoyle	Sci 240

Lab assignments will typically be assigned in class at the beginning of the week and will be due before midnight on Saturdays. You are strongly encouraged to start early and to attend the study sessions for extra practice.

You will submit you assignments electronically using the handin21 program. You may submit your assignment multiple times, and a history of previous submission will be saved. You are encouraged to submit your work regularly.

Late Policy:

Each individual will be given 2 late days for the semester, as per the CS department policy. A late day is a 24 hour extension from the original deadline. You can use one day on two assignments or both days on one assignment. This will encompass any reason - illness, interviews, many midterms in the same week, etc. Past these days, late assignments will not be accepted. You should budget your days to account for future illnesses or assignment deadlines for other courses. Even if you do not fully complete a lab assignment you should submit what you have done to receive partial credit.

The CS labs are open 24 hours a day, 7 days a week for you to use for CS21 lab assignments.

If you feel that you need an extension on an assignment (beyond your late days) or that you are unable to attend class for two or more meetings due to a medical condition (e.g., extended illness, concussion, hospitalization) or other emergency, you must contact the dean's office and your instructors. Faculty will coordinate with the deans to determine and provide the appropriate accommodations. Note that for illnesses, the College's medical excuse policy, states that you must be seen and diagnosed by the Worth Health Center if you would like them to contact your class dean with corroborating medical information.

Academic Integrity

Academic honesty is required in all your work. Under no circumstances may you hand in work done with (or by) someone else under your own name. Your code should never be shared with anyone; you may not examine or use code belonging to someone else, nor may you let anyone else look at or make a copy of your code. This includes, but is not limited to, obtaining solutions from students who previously took the course or code that can be found online. You may not share solutions after the due date of the assignment.

Discussing ideas and approaches to problems with others on a general level is fine (in fact, we encourage you to discuss general strategies with each other), but you should never read anyone else's code or let anyone else read your code. All code you submit must be your own with the following permissible exceptions: code distributed in class, and code found in the course text book. In these cases, you should always include detailed comments that indicates on which parts of the assignment you received help, and what your sources were.

Failure to abide by these rules constitutes academic dishonesty and will lead to a hearing of the College Judiciary Committee. According to the Faculty Handbook: "Because plagiarism is considered to be so serious a transgression, it is the opinion of the faculty that for the first offense, failure in the course and, as appropriate, suspension for a semester or deprivation of the degree in that year is suitable; for a second offense, the penalty should normally be expulsion." Be aware that we will be routinely running plagiarism detection software on the lab solutions of students from all sections of CS21.

The spirit of this policy applies to all course work, including code, homework solutions (e.g., proofs, analysis, written reports), and exams. Please contact me if you have any questions about what is permissible in this course.

Exam Integrity

Students must strictly adhere to the following policy, which applies to all exams taken in a Computer Science course at Swarthmore:

Exam takers must place all non-essential items at the front of the room (or other designated area). Unless otherwise permitted, students may not have any electronic devices or course materials in their possession during the entirety of the exam. This includes cell phones, tablets, laptops, smart watches, course notes, articles and books, among others. These items should be placed at the front of the room near the proctor. If you need to leave the room during the exam, you must obtain permission from an instructor first. Any non-permitted discussion or aide in regards to exam material will result in immediate forfeiture of the exam and a report to the College Judiciary Committee. Please discuss any concerns or accommodations with your instructor prior to starting the exam.

Student Support

Lauri Courtenay is the CS Department's Academic Support Coordinator. She will be working closely with our student mentors, also known as Ninjas, to help you learn how to program and think like a computer scientist. The CS21 Ninjas will assist me in class and run evening study sessions in the birds' nest (Sci 256). The CS21 Ninjas (student mentors) are: Ariel (Sky) Overdorff, Kenny Mai, Christie Little, Kendre Thomas, Rohan Hejmadi, Ayaka Yorihiro, Maleya Peterson, Shayne Rothman, Zachary Viscusi, Michael Kourakos, Tai Thonghai, and Tristan Cates.

Study Sessions

You are invited -- and encouraged -- to participate in Ninja evening study sessions to prepare for quizzes, to discuss programming concepts, and to get friendly assistance in working on lab assignments. Our CS mentoring team is dedicated to helping students, who have no prior knowledge of computer science, learn to program in Python while keeping their senses of humor intact. As an added bonus, free snacks will be provided at the sessions. The sessions are held:

Weekly Evening Ninja Sessions
Wednesdays	7—10pm	Sci Center 256
Fridays	7—9pm	Sci Center 256

Accessing the CS labs after hours

You can use your ID to gain access to the computer labs at nights and on the weekends. Just wave your ID over the microprox reader next to the lab doors. When the green light goes on, just push the door to get in (the door knob will not turn). If the green light doesn't go on, then we need to enter your microprox number into the system. Email local-staff@cs.swarthmore.edu (or see Bridget) if you have problems with this. If the building is locked, you can use your ID to enter the door between Martin and Cornell library. For this class, your ID will give you access to the labs in rooms 238, 240, and 256 and Clothier 16.

Academic Accommodations

If you believe you need accommodations for a disability or a chronic medical condition, please contact Student Disability Services (Parrish 113W, 123W) via e-mail at studentdisabilityservices at swarthmore.edu to arrange an appointment to discuss your needs. As appropriate, the office will issue students with documented disabilities or medical conditions a formal Accommodations Letter. Since accommodations require early planning and are not retroactive, please contact Student Disability Services as soon as possible. For details about the accommodations process, visit the Student Disability Services website.

To receive an accommodation for a course activity, you must have an Accommodation Letter from the Office of Student Disability Services and you need to meet with me to work out the details of your accommodation at least two weeks prior to the activity.

You are also welcome to contact me privately to discuss your academic needs. However, all disability-related accommodations must be arranged, in advance, through Student Disability Services.

How to Succeed in CS 21

• Attend class.
  The primary introduction to course material is through class lecture. Additionally, we often do lab exercises during class. This is an important part of the learning process, as these exercises give you immediate experience with the material we are covering.
• Read the material before you come to class.
  Don't worry about total comprehension, but at least get a feel for what we will be covering that week. If you have some understanding of the material coming into class, it will be easier for you to ask questions during class, rather than later when help may not be available.
• Ask questions if you don't understand.
  This means both during class and while doing lab assignments. This class continually builds on previous material, so if you don't understand something one week, it will continue to be a problem the next week, and the week after that, and so on. If you need help, ask your classmates (make sure you have read the "Academic Integrity" section below first), attend study sessions, come talk with me during my office hours, or email me your question.
• Start the lab assignments early.
  I realize this one is not always easy to do, but if you can get in the habit of doing this, you will be much better off. If you get stuck early (i.e., not two hours before it is due), there will be time to look for help. In addition, if you start early enough, you can take a break, go do something else, and come back later. I find I always have at least a few new ideas when I come back to a problem after a break. If you wait until the last minute, you can't do this.
• Practice, practice, practice.
  The only effective way to learn the material and pass the quizzes and exams is to consistently do the labs. Finish all of the assigned programs (and do some extras, for fun!). Even if you don't get them done on time, they will still help you learn the material.
• Seek help early and often.
  Because course material builds on previous material, it is essential to your success in this class that you keep up with the course material. If you are having difficulty with a programming assignment, if you didn't follow something covered in lecture, if you feel you need some extra help understanding or practicing some of the course material, or if you just want to discuss something from a lecture, an assignment, or the text, please come to my office hours.
• Attend CS21 Labs and Study Sessions.
  Lab attendance is required. The student Ninjas hold evening study sessions each week. You are encouraged to participate in these sessions. The Ninjas will help you prepare for quizzes, will provide additional instruction in programming concepts, and will provide friendly assistance on your lab assignments.

Programming Style

Programming is not a dry mechanical process, but a form of art. Well written code has an aesthetic appeal while poor form can make other programmers and instructors cringe. Programming assignments will be graded based on style and correctness. Good programming practices usually include many of the following principles:

• A comment at the top of the program that includes
  • Program authors
  • Date or Dates
  • A brief description of what the program does
• Concise comments that summarize major sections of your code
• Meaningful variable and function names
• Function comments that include:
  1. description of what function does
  2. description of input value(s) (parameter values)
  3. description of return value
• Well organized code
• White space or comments to improve legibility
• Avoidance of large blocks of copy-pasted code

Piazza

This semester we’ll be using Piazza, an online Q&A forum for class discussion, help with labs, clarifications, and announcements that pertain to all sections of cs21. You should have received an email invitation to join CS21 on Piazza. If you didn't, please let us know.

Piazza is meant for questions outside of regular meeting times such as office hours, ninja sessions, class, and lab. Please do not hesitate to ask and answer questions on Piazza, but keep in mind the following guidelines:

1. Piazza should be used for ALL content and logistics questions outside of class, lab, office hours, and ninja sessions. Please do not email instructors or ninjas with your code or questions about the assignments.
2. If there is a personal issue that relates only to you, please email your instructor.
3. We encourage non-anonymous posts (which will count towards participation), but you may post anonymously.
4. Do NOT post long blocks of code on Piazza - if you can distill the problem to 1-2 lines of code and an error message, that’s fine, but try to avoid giving out key components of your work.
5. By the same token, when answering a question, try to give some guiding help but do not post code fixes or explicit solutions to the problem.
6. Posting on Piazza counts toward your participation grade, both asking and answering!

Useful Links

Links that are related to the course may be posted here. If you have suggestions for links, let me know.

Using Unix
Basic Unix Commands
Remote access with atom