Quiz 3 Information

Quiz details

• Quiz 3 will be held on Wednesday 7/24/24, during the 6-hour window of 15:00 - 21:00 EDT

  • Boston (EDT): 3pm-9pm EDT
  • China: Thursday 6/6/24 3am-9am
  • UTC (UK time): 19:00-1:00 (+1 day)

• You will have 30 minutes for the quiz including writing your answers and submission.

• There are some sample/pratice questions at the bottom of this page. You will need to determine and write the answer(s) without a list of options to choose from.

• In addition, there will be questions that ask you to write a function or a short program, similar to the examples from class or problem sets.

Quiz Logistics

• The quiz will be conducted in the context of Gradescope. We will use the “online quiz” feature of Gradescope, in which you will type all of your answers directly into boxes within the web browser.

• You may use blank scratch paper in preparing your answers to quiz questions, but you will type your final responses into Gradescope.

• If you encounter technical errors with Gradescope during the quiz: write your answers on plain paper, scan the pages, and email them to Aaron (azs@bu.edu) as evidence of your work.

• You may not use Spyder or any other Python tools to write, test, debug, or evaluate any code.

• You may not use ChatGPT or any similar AI tools to write solutions for this quiz. We reserve the right to do a live oral exam with anyone suspected of using AI tools.

• You should take the quiz by yourself in a quiet room, without assistance from others and without using resources of any kind. Although we cannot prevent you from consulting other resources, attempting to do so will likely cause you to run out of time. Moreover, the final exam will have a live proctor; if you cannot solve the problems on your own on the quizzes, you will not be successful for the final exam.

• As this will be an independent quiz, the course staff is not available to help you with questions about the quiz during real-time. If you have questions or concerns during the quiz, write your questions or any assumptions clearly on you answer page, and we can discuss during office hours.

• Aside from the machine on which you are reading the quiz, you must turn off and put away all other electronic devices including your phone.

• You may not communicate with anyone during the quiz. You must not discuss the quiz with classmates until the entire quiz window is closed. Any discussion creates an unfair advantage to students who take the quiz a later time.

  We reserve the right to conduct a separate one-on-one oral examination with any student to verify the student’s understanding of the material.

Material covered

The quiz will focus on the material that we have discussed in class during Week 3, modules 5 and 6.

You must be familiar with concepts that were introduced in the pre-class videos, in-class discussion, or on the problem sets that were not covered in the videos or readings.

Preparing for the quiz

• One way to prepare is to review the videos and readings and class notes and make a summary of the key points in your own words. “Summarizing” the material in this way is a great way to ensure that you really understand the key concepts.

• We also encourage you to do practice problems. Options include:

  • redoing the problems from the problem sets

  • additional practice problems (below)

• When working on practice problems, try to come up with your answers on paper, rather than through a trial-and-error approach in Spyder or in another programming environment. This will be give you an experience that is similar to the one that you have during the quiz.

• Feel free to post questions about the quiz on Piazza (using the quiz3 tag).

Additional practice problems

1. Evaluate the following list comprehensions:

   a. 'a' in 'backache'

   b. [3 for x in range(6)]

   c. [2*y + 1 for y in [1, 3, 5, 7]]

   d. [x for x in range(3, 10) if x % 2 == 0]

   e [len(w) for w in ['Go', 'Terriers']]

2. Write a function count_occurences(x, values) that uses iteration to process a list of values and counts how many times the element x occurs in values. For example: count_occurences([7, [7, 4, 7, 6, 8, 5]) would return 2, and, count_occurences([3, [7, 4, 7, 6, 8, 5]) would return 0.

3. Write a function num_divisors(n) that returns the number of integers from 1 to n (inclusive) that divide n evenly. For example, num_divisors(42) should return 8, because 1, 2, 3, 6, 7, 14, 21, and 42 are all divisors of 42.

   Try solving this 2 ways:

   a. Use as list comprehension to produce the list of divisors of n, and then use len(list) to count the number of divisors of n.

   b. Use iteration and the accumulator pattern to count the number of divisors of n.

4. Use the above num_divisors(n) function in order to write a function most_divisors(lst) that takes in a list of integers lst and returns the integer from that list with the most divisors. For instance, most_divisors([2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14]) should return 12.

5. Write a function longest_string(lst) that takes in a list of strings lst as input and returns the longest string from that list. For example, longest_string(['short', 'longer', 'sesquipedalian']) should return 'sesquipedalian'.

6. Write a function cycle(s, n) that takes in a string s of '0's and '1's and an integer n and returns the string in which s has shifted its last character to the initial position n times. For example, cycle('1110110000', 2) should return '0011101100'.

   Hint: use a loop