Spring 2017 CS 1110/1111 Exam 2

Transcription

1 Spring 2017 CS 1110/1111 Exam 2 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, only modify arguments if we ask you to, etc. 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 and we ll give it due consideration during grading. Pledge On my honor as a student, I have neither given nor received help or assistance on this exam. Signed:

2 Question 1 (11 points) Fill in the following table. The first entry is done for you. If there is an error, write Error in the blank. Assume that s is 'GLAD' and d is {1:"one", "two":2}. Expression Value 1 < 2 True len(range(3,7,2)) True or False True and False len(d) 'f' in 'Fox' s[-2] 3 == '3' d['one'] s[0] == s[-len(s)] 'fun' < 'common' d.keys() Question 2 (4 points) Given the following code a, b = input('enter two numbers: ').split() a, b = int(a), int(b) which of the following would set a to 3 and b to 5? Select all that would work by circling their option letters. A. Typing 3 5 B. Typing 3,5 C. Typing 3, 5 D. Typing 3 on one line and 5 on the next 2

3 Question 3 (8 points) How many lines of output do the following programs print? for i in range(5): for j in range(5): print(i,j) Prints lines for i in range(5): for j in range(i): print(i,j) Prints lines Question 4 (12 points) The following program prints two lines, each printing the values of three variables. Write those two lines on the blanks provided. def f(a, b, c): a[0] = 3 b.append(3) c = [3, 2] print(a, b, c) a = [1, 2] b = [] c = [1, 2] f(a, b, c) print(a, b, c) First printed line: Second printed line: 3

4 Question 5 (5 points) Given two lists, return the element in the second list that has the same index as the first element 'y' in the first list. E.g., ys_pair(['x', 'yes', 'y', 'z'], [2, 3, 5, 7]) should return 5. def ys_pair(list1, list2): Question 6 (5 points) Provide one example value for x that causes the following function to return the wrong answer. It is supposed to return the same thing as the built-in function max. def biggest(x): answer = 0 for e in x: if e > answer: answer = e return answer Example value for x for which the wrong answer is returned: Question 7 (5 points) Re-write the following as a single return expression. if a < b: return True Rewite it as: elif a > 2*b: return True else: return return False Question 8 (10 points) Re-write the following using for instead of while i = 2 while i < 10: print(i) i += 1 4

5 Question 9 (15 points) The Python extended slice operator includes a step-size after a second colon, so e.g. [1, 2, 3, 4, 5, 6][::2] returns [1, 3, 5]. Write a function eslice that implements this kind of extended slice without using the extended slice operator. Accepts two arguments: a list argument and an integer n, in that order. Return a new list that contains every nth element of the list argument, starting with the first element. For example, eslice(['yes', True, 3, 3.0], 2) should return ['yes', 3]. Question 10 (15 points) Write a function named in_order that takes a single list argument; the function returns True if the elements in the list are in non-descending order. For example, in_order([1, 2, 2]) should return True, but in_order([1, 3, 2]) should return False. Do not modify the contents of the provided list. 5

6 Question 11 (10 points) Assume there exists a file stuff.csv; write a program that prints the maximum value of the third column of that CSV file. Assume the third column contains numeric values. For example, if stuff.csv contained 1,3,5,7 13,17,19,23 the program would print 19 6