CISC 121 004 Fall 2012

1. CISC 121 004 Fall 2012

2. Instructor and Teaching Assistant • Instructor: • Wendy Powley • wendy@cs.queensu.ca • Goodwin 632 • http://www.cs.queensu.ca/home/wendy • Teaching Assistant: • To be announced

3. Assistance • 2 hour class on Monday – TA and instructor will be here – ask your questions! Please do NOT be shy. • Use your peers! • TA will hold office hours once we know who he/she is – these will be announced. • I don't have set office hours – you are free to contact me via email, use the question/answer board on the Moodle or set up a time to come to see me. • From time to time, I may offer small tutorial sessions on particular topics – if this is something you are interested in, please feel free to suggest it to me!

4. Should you be in CISC 121? • CISC 121 assumes some programming knowledge • You should already know basics like: • variables • functions • data types – strings, integer, float • conditionals (if (x > 2) and NOT y then ....) • You should have experience writing some simple programs.

5. Should you be in CISC 121? • Today’s class should be a review of concepts you have learned previously (although perhaps in a different programming language) • CISC 101 (or CISC 110) is for those with little to no programming knowledge. If today’s class seems difficult to you, or the homework is difficult, please consider switching classes. • Switching classes later in the term will be difficult! • CISC 101/110 use different programming language – it will be difficult to catch up if you leave it too late.

6. CISC 121 – the “other” section • There are two sections of CISC 121 running concurrently. • They are NOT interchangeable!!! • Method of teaching will be different • Order of topics will be different • Different quizzes/assignments, marking scheme etc • However ... we are teaching all the same concepts. • You can still flee now --- but do so quickly!

7. CISC 121 – Class Format • Monday 12:30 – 2:20 – held in Jeffery 155 • lots of hands-on activities • individual & pairs • assistance provided in class • COME PREPARED– readings DONE! • And be prepared to stay – this is NOT a drop-in “lab” – it is a class. • Thursday 8:30 – 9:20 – held in Jeffery 101 • more lecture style (fill in the gaps) • quizzes

8. Marking Scheme ** if your final exam mark is less than 50%, your final will count as 80% of your mark (with assignments 8%, participation 2%, quizzes 10% )

9. Homework • Homework assignments will be given weekly – beginning today. Due on Fridays at 12:00 noon. No exceptions! • with the exception of Thanksgiving week and the last week of class • Begin work in class on Monday – finish on your own during the week. • Its ok to work with others to solve problems (and I encourage it), however, please hand in your own work. Identical (or near identical) assignments will face penalties.

10. Participation • 5% of your mark will be for participation • periodically during class I will ask you to do some activity – perhaps a survey, a short quiz or to upload some of your work. You will be marked on whether or not the task is done – not on its correctness. • SO.......if you are not in class, you will not have the opportunity to earn participation marks.

11. Textbook Required book: • Python for Software Design: How to Think Like a Computer Scientist: Allen Downey Downey book can be downloaded on-line (see Moodle)

12. Other Resources • Course notes (posted on-line) • Each week you will be asked to do some preparation prior to Monday’s class. This is mandatory – you must come to class prepared and ready to work. • Class time will be used for practical exercises -- short introductions to the topics may be given, but you are responsible for the in-depth learning on your own. • There are MANY other resources available – learn to seek them out!!! • This is one of the learning objectives of the course – resourcefulness!!!

13. The Moodle • All course material can be found on the CISC 121 Moodle • Let’s go to the Moodle ... • http://moodle.queensu.ca • Please update your profile with your first name and a picture (when you can). • Check the calendar for quiz dates! • Watch for announcements during the term on the Moodle • I will send emails & put announcements at the top of the Moodle page.

14. Programming Language/Environment Pythonis available in the Jeffery Lab – and available for download at: http://www.python.org/download/ Where does the Python name come from? Why Python? Python Version 2.7!!! (There are several versions on the lab computers – we will use 2.7). • be sure any reference material you use is Python 2, not Python 3 – there are many differences! IDLE IDE – we’ll use this in class. If you have another you prefer, please feel free to use it. http://wiki.python.org/moin/PythonEditors

15. Course Content • Basics of programming in Python • Strings, lists, iterations, loops, nested loops, conditionals • Functions, scope • File I/O • Recursion • Searching, sorting • Complexity • Dictionaries • Linked Lists • Binary Search Trees • & program structure, good programming style, commenting, problem solving, debugging etc.

16. Questions?

17. Let’s try • Find Python 2.7 & start the IDLE IDE (Python GUI) • Write the requisite “Hello World” program in the Python Shell • Open a “New Window”, write the Hello World program, save it and run it. • Explore the IDLE configurations You will probably want to bring a flash drive to class to save your work on!

18. Let’s try • Find Python 2.7 & start the IDLE IDE (Python GUI) • Write the requisite “Hello World” program in the Python Shell • Open a “New Window”, write the Hello World program, save it as hello.py and run it. • Explore the IDLE configurations You will probably want to bring a flash drive to class to save your work on!

19. Download/Upload to Moodle • Download the class files for today & save them somewhere on your computer • NOTE that any files placed anywhere other than the D drive (or a flash drive that you bring with you) will be deleted when you log out! • Extract the files • Upload your hello.py to the Moodle.

20. IDLE Editor • You will want to become comfortable with the IDLE editor – it will make your life easier! • Open ying_yang.py & run it. • ying_yang uses turtle graphics – research it if you want to know more. • Experiment with the various IDLE format commands. • check in the “Help -> IDLE help” to find out what some of the items mean. • Notice the different colours used by the editor. What do they mean?

21. IDLE Editor • Notice the indentations • Select several lines in the “yin” function and use “indent region” to indent the selected lines. • save & run • If you’re waiting ... try changing the colors of ying_yang...or some of the calculations. Relative indentation is an important part of the Python language!

22. Print Statement Try: print 7 print “Hello Put_your_name_here” print “I am ”, Put_your_age_here, “ years old” print 2 + 7 print 2 + 7, 1 + 1, 100 + 1 print 1,000,000 #what’s happening here? print 1; print 2 print “the result of 2 plus 3 plus 5 is”, 2+3+5 print evaluates each “expression” in turn and writes the resulting object to “standard output” (sdout) Strings may be quoted with double or single quotes – try it! You can even include a single quote in a double quoted string: Try printing: Welcome to Wendy’s!

23. More on Print Put these lines into a file & run: print ‘End a print statement’ , print ‘with a comma and no new ’ , print ‘line will be added’ What happens if you cut & paste this into the IDLE window? Examine the errors – correct it!

24. Arithmetic Expressions An arithmetic expression consists of operands (values) and operators (+ - * / ** %), and represents a numeric value Note: * = multiplication, / = division, ** = exponential % = modulo Try (in the python shell): 4 + 3 * 2 (4 + 3) * 22**3 11%2 #what’s this – try some more & see what happens 24%6 14%0 10/3 3/6 10.0/3 Are the results as you expected?

25. Calculations on Strings • Try adding two strings together • Try multiplying two strings together • Try multiplying a string by a scalar number • Try dividing one string by another Remember the quotes around your strings!!!! print Dog + ‘house’ #what happens?

26. Data Types • Every value has a type associated with it. • Some types: • String: “CISC 121” or ‘CISC 121’ • Integer: 99 • Floating Point (or “float”): 99.9 • Boolean: True/False

27. Find out the type of a value: Try: • type(5) • type(“five”) • type(“5”) • type(5.2) • type([2, 3]) type() is a python function

28. More Python functions Try these in the python interactive shell • print round(3.1453838, 2) • print round(3.1453838, 5) • print len(“hello”) • print len(‘#&$”*#((‘) • print len(‘’) Conversion functions convert values from one type to another: • int(‘32’) • str(32) • .......and others!

29. Storing Information • Sometimes our program may need to remember information to be used later for example: • the result of a calculation • input from a user • input from some other source -- temperature from a web site, information read from a file, cost of a stock periodically taken over time (cost, timestamp) • .....

30. Variables • Variables are locations in memory containing a value, labeled with a name • They are called “variables” because their contents can vary • We can store data in a variable • We can perform a calculation and store the results in a variable • We access stored values by using their variable names • Assignment Statements create new variables and gives them an initial value. • eg. x = 10 dog = “Fido”

31. Variable names • should be meaningful • must begin with a letter • usually begin with a lowercase letter • can contain letters, numbers and underscores Cannot be one of Python’s keywords:

32. Try: name = “Wendy” print name age = 27 print age print name, “is ”, age, “ years old” print “my age plus 10 is “, age + 10 print age age = age + 10 print age Try: p1 = “its the life in your years.” p2 = “years in your life that count, ” p3 = “In the end its not the “ Use these 3 variables to print out (in a single sentence), a wise saying.

33. Be careful! zipcode = 01000 type(zipcode) print zipcode (???????) (to figure out what’s going on try 01, 011, 0100)

34. Python is Dynamically Typed • Python is “dynamically typed” • This is different from most other languages where we state the type at declaration and variable type does not change. Try: name = “wendy” type (name) #note the type name = 100 type(name) #what type is it now? It has changed!!

35. Simple Functions • A function is a named sequence of statements that can later be “called” from elsewhere in your program. • type() is a built-in function that we’ve used, but you can (and you will!!!) write your own fuctions.

36. Sample Function Let’s write a simple function that prompts the user for the price of a meal and outputs the total amount of the meal with a 15% tip added. You should read about the differences between the “input()” and the raw_input() functions

37. You try: Write a function that prompts the user for the length and width of a rectangle and outputs the perimeter and the area of the rectangle. ....the homework for this week begins here .