Question/Answer Booklet COMPSCI 101 Page 1 of 14 THE UNIVERSITY OF AUCKLAND SUMMER SEMESTER, 2020 Campus: City COMPUTER SCIENCE Principles of Programming (Time Allowed: TWO hours) NOTE: You must answer all questions in this exam. No calculators are permitted. Answer in the space provided in this booklet. There is space at the back for answers which overflow the allotted space. Surname Forenames Preferred Name (if different to forenames) Student ID Username Q1 (/12) Q4 (/16) Q7 (/10) Q2 (/20) Q5 (/12) TOTAL Q3 (/18) Q6 (/12) Question/Answer Booklet COMPSCI 101 ID: ……………… Page 2 of 14 Question 1 (12 marks) a) In the docstring of the program below, add a short description (15 words or less) of what the program does. """ """ def process_digits(number): digits = str(number) result = -1 for digit in digits: if int(digit) > result: result = int(digit) return result def main(): print(process_digits(234)) main() (6 marks) Question/Answer Booklet COMPSCI 101 ID: ……………… Page 3 of 14 b) Rewrite the following function using descriptive variable and function names. def who_knows(something): for xxxx in range(len(something) - 1, -1, -1): a_thing = something[xxxx] if a_thing < 0: something.pop(xxxx) def ( ): (6 marks) Question/Answer Booklet COMPSCI 101 ID: ……………… Page 4 of 14 Question 2 (20 marks) a) Give the output produced when the following program is executed. def main(): print("A", end = " ") do1() def do1(): do3() print("B", end = " ") do2() def do2(): print("C", end = " ") def do3(): do2() print("D", end = " ") main() (6 marks) Question/Answer Booklet COMPSCI 101 ID: ……………… Page 5 of 14 b) Using the code trace technique taught in lectures, perform a code trace on the following program and show the output. def first(number): total = 6 number = second(number + total) print("1.", number) return number % 3 def second(value): print("2.", value) if value % 2 == 0: value = value + 3 else: value = value + 2 return value def main(): num = 5 result = first(num) print("3.", result) result = second(result) + num print("4.", result) main() (14 marks) The output: Question/Answer Booklet COMPSCI 101 ID: ……………… Page 6 of 14 Question 3 (18 marks) a) Complete the output produced when the following main() function is executed. def main(): a_list = [1, 4, 3] do_something1(a_list) print("a_list:", a_list) def do_something1(list1): list2 = list1 extras = [2, 1, 4] for element in extras: list2.append(element) a_list: (6 marks) b) Complete the output produced when the following main() function is executed. def main(): a_list = [3, 7] do_something2(a_list) print("a_list:", a_list) def do_something2(list1): list2 = [4, 3] for element in [2, 5]: list1.append(element) list1 = list2 a_list: (6 marks) Question/Answer Booklet COMPSCI 101 ID: ……………… Page 7 of 14 c) Given the following code, what is the type of the three Python objects: object1, object2 and object3? a_list = [1, '457', 4, 'True'] a_dict = {"strangely": 2, "happy": 4} object1 = a_list[2] / 2 object2 = [a_list.pop(2) == a_dict["happy"]] object3 = len(a_list[1] * 3) * a_dict["strangely"] object1: object2: object3: (6 marks) Question/Answer Booklet COMPSCI 101 ID: ……………… Page 8 of 14 Question 4 (16 marks) a) What are the contents of the file “Output.txt” after the following program is run? def main(): data_dict = {850:["Kim", "Lucy"], 700:["Ken", "Mele"], 450:["Ronald"],1000:["Gill", "Bart"], 200:["Alfonso"]} filename = "Output.txt" write_data(filename, data_dict) def write_data(filename, data_dict): key_list = list(data_dict.keys()) key_list.sort() key_list.reverse() output_stream = open(filename, "w") for key in key_list: values = data_dict[key] values.sort() for value in values: output_stream.write(value + " - " + str(key) + "\n") output_stream.close() main() (9 marks) Question/Answer Booklet COMPSCI 101 ID: ……………… Page 9 of 14 b) Give the output produced when the following main() function is executed. Show all your working. def main(): number = 0 for i in range(5): number += 1 for j in range(i): number += 1 print(number) (7 marks) Question/Answer Booklet COMPSCI 101 ID: ……………… Page 10 of 14 Question 5 (12 marks) a) Consider the function below named get_code()that takes a string as a parameter and returns a code consisting of 3 unique characters chosen from the parameter at random. The same character does not appear in the code more than once. The parameter string has more than 3 characters and contains no repeated letters. For example, the following statement: print(get_code('ABCDE')) could possibly produce: DEA The variable names in this function have not been chosen using good style considerations. Rewrite the function in the answer box below using descriptive variable names that conform to the style guidelines outlined in lectures and labs: def get_code(w): a = '' for i in range(3): p = random.randrange(0, len(w)) a += w[p] w = w[0:p] + w[p+1:] return a def get_code( ): (6 marks) Question/Answer Booklet COMPSCI 101 ID: ……………… Page 11 of 14 b) Consider the function below named swap_halves(numbers)which takes a list of integers as a parameter and returns a new list that has every element in the second half of the original list swapped with every element in the first half of the original list. def swap_halves(numbers): mid = len(numbers)//2 return numbers[mid:] + numbers[0:mid] In the box below, write two doctests for the swap_halves() function - one that fails the test and one that passes the test. def swap_halves(numbers): """ """ (6 marks) mid = len(numbers)//2 return numbers[mid:] + numbers[0:mid] import doctest doctest.testmod() Question/Answer Booklet COMPSCI 101 ID: ……………… Page 12 of 14 Question 6 (12 marks) a) Assume that the variable, value, has been initialised to some integer value. Write a boolean expression which tests if value is exactly between 2 and 12 (both inclusive). (3 marks) b) Assume that the variable, value, has been initialised to some integer value. Write a boolean expression which tests if value is exactly divisible by 13 but not divisible by 5. (3 marks) c) Assume that the string variable, city, has been initialised to some value. Write a boolean expression which tests if city is either “Gore” or “Auckland” or “Dunedin”. (3 marks) d) Assume that the string variable, word, has been initialised to some value. Write a boolean expression which tests if word contains the letter “b” and does not contain the letter “d”. (3 marks) Question/Answer Booklet COMPSCI 101 ID: ……………… Page 13 of 14 Question 7 (10 marks) As accurately as possible, in the window below, show what is drawn when the following program is executed. The grid lines have been drawn in the window to help you. The gap between adjacent gridlines is 10 pixels. def draw_pattern(a_canvas, left, top, size): number_of_shapes = 3 for count in range(number_of_shapes): rect = (left, top, left + size, top + size) a_canvas.create_rectangle(rect) left = left + size top = top + size size = size + 10 def main(): ... draw_pattern(a_canvas, 10, 10, 10) window.mainloop() main() (10 marks) 10 20 30 40 50 60 70 80 90 100 110 120 10 20 30 40 50 60 70 Question/Answer Booklet COMPSCI 101 ID: ……………… Page 14 of 14 OVERFLOW PAGE (If you have used this page, please indicate clearly under the relevant question that you have overflowed to this page) ________________________________________
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