UNIVERSITY OF TORONTO SCARBOROUGH. Fall 2015 EXAMINATIONS. CSC A20H Duration 3 hours. No Aids Allowed

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1 Student Number: Last Name: First Name: UNIVERSITY OF TORONTO SCARBOROUGH Fall 2015 EXAMINATIONS CSC A20H Duration 3 hours No Aids Allowed Do not turn this page until you have received the signal to start. (In the meantime, please fill out the identification section above, and read the instructions below carefully.) This final examination consists of 7 questions on 15 pages (including this one). When you receive the signal to start, please make sure that your copy of the examination is complete. Answer each question directly on the examination paper, in the space provided. (If you need more space for one of your solutions, use the blank page and indicate clearly which part of your work should be marked.) Be aware that concise, well thought-out answers will be rewarded over long rambling ones. Also, unreadable answers will be given zero (0) so write legibly. In the programming questions, assume all input is valid. Make sure to indent your code properly. Your code will be marked based on correctness and style. Some questions in the exam follow on other questions. When answering a question you may assume that all functions in the preceding questions have been implemented correctly, and you may make use of these functions. # 1: / 8 # 2: / 10 # 3: / 20 # 4: / 15 # 5: / 27 # 6: / 10 # 7: / 10 TOTAL: /100 Good Luck! Total Pages = 15 Page 1 over...

2 Question 1. [8 marks] Consider the following Python program. def f(a, b): """missing docstring""" print(a, b) return b == 1 or a > 1 def g(x, y): """missing docstring""" x[1] = y return x def h(x, y, z): """missing docstring""" if f(y, z): return g(x, y) else: return g(x, z) Fill in the outputs for the Python shell session in the boxes below (assuming appropriate imports have been done). If you think Python will raise an Error, write error. >>> h([2,4,0], 5, 10) [0, 10, 4] >>> h([2,1,0], 1, 24) 1 55 [2, 55, 0] >>> h("456", "a", "b") z y Error If you thought that Python raised an Error for any of the above, explain what caused the error. There are two solutions that we can accept - one,we can t compare an int to a str (in f(a, b) and a > 1) or another potential error is assigning x[1] a value (x is a string which is immutable). Total Pages = 15 Page 2 cont d...

3 Question 2. [10 marks] The following implementation is incorrect it has several bugs. Your task is to identify and fix them in the code below. Notice that the headers and the docstrings are all correct; only the implementation is faulty. The errors are not syntax errors, but rather logical errors. Correct the code directly in the space provided. def earlier(str1, str2): (str, str) -> bool Soln. Return if str1 comes earlier in the alphabet than str2, and otherwise. Assume that str1 and str2 only contain characters from the alphabet. >>> earlier( anna, banana ) >>> earlier( anna, anana ) >>> earlier( Anna, banana ) >>> earlier( Anna, anana ) print( str1.upper() < str2.upper() ) return (str1.upper() < str2.upper()) def is_sorted_alpha(lst): (list of str) -> bool Return if lst is sorted in alphabetical order. Assume the strs in lst only contain characters from the alphabet. >>> is_sorted_alpha([]) >>> is_sorted_alpha([ apple ]) >>> is_sorted_alpha([ apple, apple, banana, cantaloupe, orange ]) >>> is_sorted_alpha( apple, banana, orange, melon ]) for i in range(len(lst)): if earlier(lst[i], lst[i + 1]): return Soln. for i in range(len(lst)-1): if earlier(lst[i+1], lst[i]): return return Total Pages = 15 Page 3 over...

4 Question 3. [20 marks] In this question your task is to design and implement a function check password that takes a str as input, and returns a bool that is if the input str contains at least 1 numeric value, 1 lower case letter and 1 upper case letter. For example, given a string TopSecret, the function should return and given string TopSecret15 would return. In the last part of the question, you will write an interactive program that uses the function check password. Part (a) [1 mark] Write the header of the function check password. def check_password(s): Part (b) [3 marks] Write the beginning of a docstring of the function: the types and the function description. """(str) -> bool Return a bool that is if the string contains a digit, an upper case letter and a lower case letter and otherwise. Part (c) [6 marks] Write the doctests for the function. Remember that the purpose of doctests is to make sure that your function works for any possible input. You may use c instead of the function name check password to save time. Hint: you should have at least 6 doctests. >>> check_password( ) >>> check_password( x ) >>> check_password( Ab ) >>> check_password( 9 ) >>> check_password( A ) >>> check_password( A9 ) >>> check_password( 0a ) >>> check_password( ba1 ) """ Total Pages = 15 Page 4 cont d...

5 Part (d) Write the implementation of the function. has_digit = has_lower = has_upper = for c in s: if c.islower(): has_lower = elif c.isupper(): has_upper = elif c.isdigit(): has_digit = return has_lower and has_upper and has_digit Part (e) Write a program (complete the part under the main block) that behaves as follows. It repeatedly asks the user for an input string for a password until the user gives a string that has one upper case character, one lower case character and one digit. Enter a password with at least one upper, one lower and one digit: csca20 Your password csca20 is not valid. Enter a password with at least one upper, one lower and one digit: CSCA20 Your password CSCA20 is not valid. Enter a password with at least one upper, one lower and one digit: csca20 Accepted! Complete the program below: if name == main : p = input("please, enter a password containing one upper, one lower and one digit:") while not check_password(p): print( Your password %s is not valid. %(p,)) p = input("please, enter a password containing one upper, one lower and one digit:") print( Accepted!) Total Pages = 15 Page 5 over...

6 Question 4. [15 marks] For this question you will be writing a program related to the frequency of the length of words in the English language. You will write the functions described below. You may assume that all the input has had all punctuation and numeric values removed. Complete the following functions according to their docstring descriptions. As required on your assignments, you must avoid duplicate code by having your functions call others when appropriate. A portion of your mark will be based on code reuse. Note that if you cannot complete one function you can still complete the others. Part (a) def list_to_dict(word_list): (list of str) -> dict Given a list of str (a list of English words) return a dictionary that keeps track of word length and frequency of length. Each key is a word length and the corresponding value is the number of words in the given list of that length. >>> d = list_to_dict([ This, is, some, text ]) >>> d == {2:1, 4:3} >>> d = list_to_dict([ A, little, sentence, to, create, a, dictionary ]) >>> d == {1:2, 6:2, 8:1, 2:1, 10:1} d = {} for word in word_list: if len(word) in d: d[len(word)] += 1 else: d[len(word)] = 1 return d Another solution is: d = {} for word in word_list: d[len(word)] = d.get(len(word), 0) + 1 return d Total Pages = 15 Page 6 cont d...

7 Part (b) def add_dicts(d1, d2): (dict, dict) -> dict Parameters d1 and d2 are dicts where each key is an int and each value is an int. Return dict d1 with the contents of d2 added to d1. More concisely, if key k is in d1 and in d2, update d1[k] to be the sum of d1[k] and d2[k]. If d2 has a key that is not in d1, add the key value pair from d2 to d1. >>> d1 = {1:1, 2:1, 3:2} >>> d2 = {1:3, 3:1, 4:1} >>> d = add_dicts(d1, d2) >>> d == {1:4, 2:1, 3:3, 4:1} for key in d2: d1[key] = d1.get(key, 0) + d2[key] return d1 Part (c) def file_to_dict(filename): (str) -> dict Open the file of the given filename. The contents of the file is English text. Return a dictionary that keeps track of word length and frequency of word length in the file. Each key is a length of word and the corresponding value is the number of words in the given file of that length. You may assume there is no punctuation or numeric values in the file and that words are separated by spaces. or f = open(filename, r ) d = {} for line in f: word_list = line.split( ) list_dict = list_to_dict(word_list) d = add_dicts(d, f.close() return d list_dict) f = open(filename, r ) d = {} word_list = f.read().split( ) d = list_to_dict(word_list) f.close() return d Total Pages = 15 Page 7 over...

8 Question 5. [27 marks] Complete the following short answer questions. Part (a) [3 marks] Explain what mutable means. Give an example of a type that is mutable and a type that is immutable. Mutable means that the type can be altered. Lists are mutable as are dictionaries, strings and tuples are not mutable. Part (b) [4 marks] Consider the following code in the shell and fill in the blank lines (i.e., the values of variables M, N, L and N again). >>> L = [1, [1, 2], 3] >>> M = L >>> N = L[:] >>> L[0] = 0 >>> M >>> N >>> L[1][0] = 8 >>> L >>> N >>> # END OF QUESTION Soln. >>> M [0, [1, 2], 3] >>> N [1, [1, 2], 3] >>> L [0, [8, 2], 3] >>> N [1, [8, 2], 3] Part (c) Consider the following code: 1 def do_it(x, y): 2 print([x, y]) 3 4 my_list = do_it(1, 2) 5 print(my_list) What does line 5 display? Explain your answer. nothing. do it doesn t return anything. Total Pages = 15 Page 8 cont d...

9 Part (d) Complete the function according to it s docstring. def clean(data_list): (list of str) -> list of int Given a list of str where each str has only numeric characters and possibly leading and trailing white space, return a list of int. >>> clean([ 23, 4, 55 ]) [23, 4, 55] L = [] for item in data_list: L.append(int(item.strip())) return L Part (e) Fill in a complete docstring for the following function. def unknown(l): (list) -> bool Return true if each item in L is twice the previous item and otherwise. >>> false example >>> true example i = 0 n = len(l) while i< n-1: if L[i+1]!= 2*L[i]: return i += 1 return Total Pages = 15 Page 9 over...

10 Part (f) Complete the function according it s docstring. def decrypt(characters, code): (list of str, list of int) -> list of str Given a list of characters and a list of ints representing indices, return a list of chars that is constructed by replacing each int in the code list with the char from the characters list at that index. >>> decrypt([ a, 2, s, c, 0 ], [3, 2, 3, 0, 1, 4]) [ c, s, c, a, 2, 0 ] >>> decrypt([ O, H ], [1, 0, 1, 0, 1, 0]) [ H, O, H, O, H, O ] for index in range(len(code)): code[index] = characters[code[index]] return code Total Pages = 15 Page 10 cont d...

11 Question 6. [10 marks] A university student database is being used for grade maintenance, exam and course scheduling purposes. Two tables are being used, Student and Courses. CREATE TABLE Student(Name TEXT, StudentID INTEGER, Grade REAL, Course TEXT, Section INTEGER) CREATE TABLE Courses(Course TEXT, Section INTEGER, Day TEXT, Time TEXT) An example of rows in the Student table: An example of rows in the Courses table: Cathy Smith CSCA20 1 Cathy Smith CSCB09 2 Shirley Martin CSCA20 1 CSCA20 1 Monday 2:10 CSCB09 1 Wednesday 9:10 CSCB09 2 Tuesday 1:10 The Courses table contains one row per course section (assume each section meets only once per week). For example, if MATA32 has two sections, there will be two rows for MATA32. In the Student table, there is one row for each course that a student is enrolled in. The Grade field contains the student s grade in that course. Write an SQL query to retrieve the data described below from the database. Note: you do not need to write any code to connect to the database; you only need to write the SQL query (e.g., SELECT... ). Part (a) [2 marks] The StudentID of students taking CSCA20. SELECT StudentID FROM Student WHERE Course = CSCA20 Part (b) [2 marks] The timetable of each student. In other words, the name of the student, their courses and their course day and time. SELECT Student.Name, Courses.Course, Courses.Day, Courses.Time FROM Student JOIN Courses WHERE Student.Course = Courses.Course AND Student.Section = Courses.Section Part (c) [3 marks] The names of Courses and the average Grade of the students enrolled in each course. SELECT Student.Course, AVG(Student.GPA) From Student JOIN Courses WHERE Student.Course = Courses.Course GROUP BY Student.Course or SELECT Courses.Course, AVG(Student.GPA) From Student JOIN Courses WHERE Student.Course = Courses.Course GROUP BY Courses.Course Part (d) [3 marks] Courses that have the same start time on the same day. SELECT A.Course, B.Course FROM Courses A JOIN Courses B WHERE A.Time = B.Time AND A.Day = B.Day AND A.Course!= B.Course Total Pages = 15 Page 11 over...

12 Question 7. [10 marks] This question has you write a program to manage student time tabling and uses the database from Question 6. The question has two parts and relies on a database that has already been created and populated with the following tables: CREATE TABLE Student(Name TEXT, StudentID INTEGER, Grade REAL, Course TEXT, Section INTEGER) CREATE TABLE Courses(Course TEXT, Section INTEGER, Day TEXT, Time TEXT) You may find the following function helpful: def run_query(db, q, args=none): Run the query q on database db and return the result. args is a tuple of arguments for the query. If provided, con = sqlite.connect(db) cur = con.cursor() if args == None: cur.execute(q) else: cur.execute(q, args) result = cur.fetchall() cur.close() con.close() return result Part (a) [4 marks] Complete functions search course (below) and insert student (on the next page) according to their docstring descriptions. def search_course(db, course_name): Retrieve the Section, Days and Times for the Course course_name (a str) from database db, and return a list of strs where each str is of the form Section Day Time for each section of that course. result = run_query(db, SELECT Section, Day, Time FROM Courses Where Course = (?), (course_name,)) day_time = [] for item in result: day_time.append(str(item[0]) + " " + item[1] + " " + item[2]) return day_time Total Pages = 15 Page 12 cont d...

13 def insert_student(db, course_name, section, student_name, studentid): Insert a new row into the table Student of database db with Name student_name, StudentID studentid, Course course_name, Section section and Grade of 0. # Connect to the database con = sqlite.connect(db) cur = con.cursor() # Insert the new row into the Student table # COMPLETE THIS LINE: cur.execute( ) cur.execute(insert INTO Student VALUES(?,?,?,?,?), (student_name, studentid, 0, course_name, section)) cur.close() con.commit() con.close() Part (b) [6 marks] Write a program that allows a student to add a course to their timetable. Your program will first prompt the user to enter their name, student ID and course request. Using this information, your program should then display for each section, the section number, the day and time and prompt the user to select one. Your program should then add the course to the database for the given student with an initial grade of 0. The database, timetable.db has already been created and populated with data. A sample interaction with a user may look like this: Enter your name: Anna Bretscher Enter your student ID: Enter your course request: CSCB09 Please select one of the following options (enter a section number): 1 Wednesday, 9:10 2 Tuesday, 1:10 1 When the user enters a section, your program should insert a new row in the table Student with the student information, course name and section to indicate that the student has enrolled in a section. After your program completes, the Student table should include a line for the new course request. It could look like this: Total Pages = 15 Page 13 over...

14 Cathy Smith CSCA20 1 Cathy Smith CSCB09 2 Shirley Martin CSCA20 1 Anna Bretscher CSCB09 1 We have provided some starter code to get you started and lay out the steps you need to complete. Make sure to fill in the code as indicated by the comments and to use the variable names defined. You should call the functions search course and insert student as needed. if name == " main ": db = time_table.db # Prompt user for name, student id and course # # ADD CODE BELOW name = input( Please enter your name. ) id = input( Please enter your student id. ) course = input( Please enter your course request. ) # Find the course sections, times and days for the requested course in the timetable # by calling function search_and_display. # ADD CODE BELOW options_list = search_course(db, course) # Give the user options for the course timetable and prompt for their section choice # ADD CODE BELOW options_str = for item in options_list: options_str = options_str + item + \n section = int(input(options_str)) # Insert the student data into the database by calling insert_student # ADD CODE BELOW insert_student(db, course, section, name, id) insert_student(db, course, fieldvalues[0], fieldvalues[1]) Total Pages = 15 Page 14 cont d...

15 Total Marks = 100 Total Pages = 15 Page 15 End of Solutions

UNIVERSITY OF TORONTO SCARBOROUGH. Wnter 2016 EXAMINATIONS. CSC A20H Duration 2 hours 45 mins. No Aids Allowed

Student Number: Last Name: First Name: UNIVERSITY OF TORONTO SCARBOROUGH Wnter 2016 EXAMINATIONS CSC A20H Duration 2 hours 45 mins No Aids Allowed Do not turn this page until you have received the signal