1 Fall 2017 CS 1110/1111 Exam 3

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1 1 Fall 2017 CS 1110/1111 Exam 3 Bubble in your computing ID in the footer of this page. We use an optical scanner to read it, so fill in the bubbles darkly. If you have a shorter ID, leave some rows blank. In case we have trouble with the scanner, please also legibly print Your name: Your computing ID: Please observe the following directions throughout the exam: Write legibly; we deduct points if we are unsure what you wrote. Indentation and punctuation do matter. Write on the lines, where possible. If you need to insert a line between two you ve written, make it clear that that is what you are doing. We grade one page at a time. Do not spill answers onto another page. Don t add features we didn t request: only print if we ask you to print, etc. Any code we ask you to explain could have an error. If so, write Error in place of the usual answer, and indicate where in the code the error is generated. The exam is being given in multiple locations simultaneously, so we cannot fairly answer student questions during the exam. If you find a question ambiguous or unclear, write that down on your exam next to the question and we ll give it due consideration during grading. 1.1 Pledge [1 pt] On my honor as a student, I have neither given nor received help or assistance on this exam. Signed: 1.2 Bubble [2 pts] Enter your computing ID, one symbol per row, top-to-bottom; if you have a short ID (like up3f) leave a row blank on the appropriate side of the digit row.

2 2 Question [10 pts] Finish the following table. Expression Value Type float '123'[1] len('is a') 2 < 3 4 / 2 (1, 3) 3 Question [6 pts] Finish the following table. Assume the user types 3 each time they are asked for input. Statement Output x x = "2" x = 2 None x = 'hi' x.upper() x = len(input('y: ')) x = list('bac') x.sort() 4 Question [3 pts] What value is assigned to answer after execution of statement answer = ((4 // 8) * (2 ** 2)) / 2? 2

3 5 Question [8 pts] For each loop, give a value for x for which the loop would run forever (e.g., a valid answer format is x = range(1000) ), or write terminates if no such x exists. Note: if you pick a value for x that will cause an error in the code, you will not get credit for that part. while True: if x < 10: break x /= 2 for i in x: if i in x: print(i) i -= 1 while x!= 1110: y = x*x print(y - x) x += 1 while len(x) >= 0: y = x.pop() z = y + 1 x.append(z) Answer: Answer: Answer: Answer: 6 Question [4 pts] Suppose you are asked to test a function named overlap; overlap(a, b) is supposed to return a list of the items that are in both a and b, without duplicates, in the order those items first appear in b. If you could only use four of the following test cases, which four should you pick? Write your four selections letters in the spaces provided, in any order. (There is more than one correct solution to this question) A. overlap([], []) B. overlap([1, 2], [3, 4]) C. overlap([1, 1], []) D. overlap([], [1, 1]) E. overlap([1, 1], [1, 1]) F. overlap([1, 2, 3, 2, 1], [3]) G. overlap([1, 2, 3, 2, 1], [2]) H. overlap([1, 2, 3, 2, 1], [3, 1, 2]) I. overlap([1, 2, 3, 2, 1], [2, 1, 2]) Test case: Test case: Test case: Test case: 7 Question [4 pts] Assume that file.txt does not exist when we first run the following program, and that we then run the program twice in a row. What will file.txt contain after the second run? f = open('file.txt', 'w') print('a line of text', file=f) f.close() 3

4 8 Question [8 pts] Assume noglobal.py defines several functions, none of which use the word global. For each program below, circle could change if it is possible for the function in noglobal to cause the two print statements to print different things or can t change if that can t be the case. import noglobal x, y = 2, 3 print(x, y) noglobal.change1(x, y) print(x, y) import noglobal x = [2, 3] noglobal.change2(x) import noglobal x = "2, 3" noglobal.change3(x) import noglobal x = [1, 2, 4] noglobal.change1(x[1]) could change could change could change could change can t change can t change can t change can t change 9 Question [8 pts] Put True or False in each cell of the following table. Assume the things discussed are non-empty. Note: if we can t tell if you wrote T or F (e.g., TF), we ll mark it wrong. has a first element can have duplicates list str dict s keys dict s values 10 Question [4 pts] Given the following file: Have a happy holidays We hope you enjoyed CS CS > other majors Which one of the following regex expressions will match each of the the first 2 lines, but not the third? A. [A-Z][^A-Z]* B. [A-Za-z ]+ C. [^>] D. [^>]? 4

5 11 Question [10 pts] Below are listed several function and method invocations. In the blanks provided, indicate which ones you d use in what order to open a web page from a URL stored in the variable url and make a list of the commaseparated values of its first line, with no \n at the end of the last cell. For example, if the web page began species,country,population ectopistes migratorius,usa,0 we want to retrieve ['species', 'country', 'population']. Write integers in the blanks below, with 1 for the first invocation you d use, 2 for the second, etc. Leave unused parts blank. You might find it easier to write the code out and then fill in the blanks decode('csv') decode('utf-8') open(url) open("url") read() readline() split() split(',') strip() strip(',') urlopen(url) urlopen("url") 12 Question [9 pts] For each regular expression and example text, put a box around the parts of the example text that finditer would find. For example, if tt was found in 'letter', you d box in 'letter'. re.compile( ).finditer( ) '[1-9][0-9]+' '[^a-za-z]+' '(the) ((a an) [0-9])' 'One can also be written 1, 01, 1.0, and 100e-2' 'Shorter example.' 'an 1 and a 2 and the 3 as well' 13 Question [4 pts] The following code will raise an Exception. On what line will the exception be raised, and what causes it? word = "grumpy" def f(): print(word) word = "happy" print(word) f() print(word) 5

6 14 Question [7 pts] Depending on what the user types, not all of the lines in the following program will be executed. In each of the seven comments in the following program, write A if the commented line runs for All inputs, S if it runs for Some input but not others, and N if it Never runs. try: fname = input('type a file name: ') # thing = open(fname) print('thanks') # except: print('no such file') # def f(x): if x > 0: return x # else: return -x # return 2*x # f(int(input('a number: '))) # 15 Question [4 pts] List two benefits of writing functions when programming. 16 Question [5 pts] Complete the line of code to make the following list: [2, 5, 8, 11] Answer: made = list(range( )) 6

7 17 Question [10 pts] Consider the following gamebox program import pygame import gamebox camera = gamebox.camera(800,600) score = 0 def tick(keys): global score camera.clear('white') score += 1 box = gamebox.from_text(400, 200, "Score is: " + str(score), "Arial", 40, "black") box2 = gamebox.from_text(400, 300, "Keep Playing", "Arial", 40, "black") camera.draw(box) camera.display() ticks_per_second = 40 gamebox.timer_loop(ticks_per_second, tick) Draw what the screen will look like 3 seconds into the program running: 7

8 18 Question [6 pts] What does this code output? def f(x, l=[]): for i in range(x): l.append(i*i) print(l) f(3) f(3, [3, 2, 1]) 19 Question [10 pts] Execution of these two Python statements: print(perimeter("triangle", 3, 1, 5)) print(perimeter("quadrilateral", 4, 3, 1, 2)) produces the output: The triangle's perimeter is 9. The quadrilateral's perimeter is 10. Write function perimeter. 8

9 20 Question [12 pts] Write a program that simulates dealing cards from a 52 card deck to two card players, then displays the cards in each player s hand. In particular, 1. Create the deck, represented by the integers 0 through Shuffle the deck using random.shuffle(deck) (you must use random.shuffle, not some other method; recall that deck must be mutable for random.shuffle(deck) to work). 3. Deal player 1 the first card, player 2 the second, player 1 the third, etc., so that each gets 5 cards. An example output (which will be different each run because of randomness) might be [1, 23, 21, 42, 0] [19, 38, 7, 31, 50] import random 9

10 21 Question [15 pts] Write a program that prompts the user to enter an integer between 1 and 100, inclusive, and stores that integer in a variable named n. The program should ensure that the input is an integer in the specified range. If the user provides a non-integer or an out-of-range integer, display an error message (with a different message for each kind of error) and ask again, continuing until a valid input is provided. 10