---
title: Homework 6
tags: Homeworks-F23, 2023
---

# Homework 6: Python Basics
### Due: Friday, April 12 at 11:59 pm

### Setup
You should have VSCode set up from the first week of the course. In case you don't, refer to the [VSCode Installation and Setup Guide](https://hackmd.io/@cs111/lab0-s24)
- Create a python file called `hw6_code.py` to include your code.
- Create a python file called `test_hw6.py` and put the following lines at the top of that file:

import pytest
from hw6_code import *

All of the tests that you write should be written in `test_hw6.py` as `assert` expressions in functions that start with `test_`.

### Remember your resources!
- [Working with VSCode for CS111](https://hackmd.io/PfF1gP5aTEGcFBKpOoRG5A?view)
- [Python documentation](https://docs.python.org/3.11/)
- [TA hours](https://brown-csci0111.github.io/pages/calendar)
- [EdStem](https://edstem.org/us/courses/54800)
- [Python Testing and Clarity Guide](https://hackmd.io/@cs111/python_guide)

## Big Picture

The goal of this assignment to give you practice with the basics of writing list-processing programs in Python. It mostly follows what we've done in class, while also showing a couple of useful Python built-in functions. Everything you need for this will have been covered by the end of class on 4/5, but we'll follow up on testing with mutatation early next week.

## The Assignment -- Election Time

:::warning
Make sure to only use Python concepts we've talked about in lecture when solving these problems. In particular, if you have other Python knowledge of other techniques, don't use them here if you want full credit.

In particular, don't use the built-in Python `count` function. That defeats the point of the problems.

#### **Also, make sure that your inputs for each function are in the order that they are mentioned in the directions. Even if your functions are correct, if your inputs are not in the correct order, it will fail the autograder.**

The Autograder we use for Python assignmens gives slightly different error output than the Autograder we used for CS111. If you encounter an error, double-check your function names and inputs. Also make sure that you can run your code and your testing code in VSCode without error. If that doesn't resolve the issue, make a post on Ed with a link to your submission.
:::

CS111 is conducting a vote for the best frog character. We're going to write some programs to tally votes. We'll represent a vote as a single `string` containing the name of the frog that got voted for. We'll represent the collection of votes recorded by a single voting machine as a `list` of votes (list of `string`).

:::warning
For every function we ask you to write, you should have a corresponding testing function in `test_hw6.py`. Name each test function the same as the original function but with `test_` prepended. In other words, the tests for a function `check_votes` would be in a function called `test_check_votes`.
:::

### Part 1: Basic Vote Counting

**Task 1:** Write a function called `name_matches`. It should take in a `vote` (string) and a `name` (string). It should return a boolean indicating whether the vote is for the given name, regardless of how either vote or the name have been capitalized.

*Note: You can convert a string `s` to lowercase in Python by writing `s.lower()`. As in Pyret, you have Boolean operators `and`, `or`, and `not`. Equality is checked using `==` (and inequality using `!=`)*

**Task 2:** In `hw6_code.py`, write a function called `any_votes_for` that takes in a name and a list of votes and returns a `boolean` indicating whether any of the votes were for the given name (case insensitive). Your solution should use a `for` loop.

**Task 3:** In `hw6_code.py`, write a function `count_votes_for` that takes in a name and a list of votes. It should return the number of votes that were for the given name (case insensitive). Your solution should use a `for` loop.

**Task 4:** In `hw6_code.py`, write a function called `got_more_votes` that determines which of two names got more votes. Your function should take in two names and a list of votes. It should return the name that got more votes (case insensitive). If there is a tie, return the string `“tie”`.

### Part 2: Recording Votes

**Task 5:** In `hw6_code.py`, write a function to record a new vote. Your function should be called `record_vote`, and take in a list of votes and a string representing a new vote. It should add the new vote to the end of the list of votes. The function **should not return anything!**

The list of votes is *mutable*, so rather than returning a new list, this function can directly modify the original list to add a new vote. The examples in the [list documentation](https://docs.python.org/3/tutorial/datastructures.html) might be helpful here.

:::spoiler *Hints on testing this function*
Remember that pytest allows us to write any Boolean expression and run it as a test by preceding it with an `assert` statement. We can also create new variables (such as the length of the input list before running `record_vote`) and use these variables in our `assert`ions. How can you write Boolean expression(s) that test whether a name was added to the end of a list? We will also see a few examples of this in class on Monday 4/8.
:::

### Part 3: Election Integrity

Voting is a topic for which people are reasonably concerned about representation, access, and accuracy (among other things). Not surprisingly, there are many arguments and proposals regarding how to properly use computing technology as part of elections: should we vote on computers so they can count ballots? allow voting online? use digital scanners to process votes marked on paper? And so on. Each option offers benefits and risks around participation in, and accuracy of, elections.

**Task 6:** - Read this brief article on the use of [internet voting in Estonia](https://time.com/5541876/estonia-elections-electronic-voting/). The article has a quote on "paper, plus audits," as a strategy for keeping elections secure. VerifiedVoting.org is an organization of experts on election security and election technology. Take a look at their [issues page](https://verifiedvoting.org/issues/) and read the brief summaries of the issues. (Nothing to write for this task.)

With people concerned about the validity of the election results, the decision has been made to run some checks against the votes to see if they appear plausible.

One issue is that write-in votes can be ambiguous. Imagine an election in which two people with the first name "Ruth" have been trying to get elected. Some votes have come through for "Ruth Achebe", some for "Ruth Flynn", and some for just "Ruth". The "Ruth" votes need to get handled for accurate results.

Someone has proposed counting "Ruth" votes that have a last name, using the presence of a space in the name string to indicate whether a vote has both a first and a last name.

**Task 7:** Write a function `clean_votes` that takes a list of votes and returns a new list of votes containing only the votes from the original list that contain at least one space (represented by the string `" "`). Your solution should use a `for` loop. *Hint: in class, we saw a `for` loop being used to update a running sum variable. How can you use a `for` loop to build out a new list to return?*

**Task 8:** Write a `test_clean_votes` function (in the `test_hw6.py` file) that explores various scenarios in which this specific approach would and wouldn't behave as we expected. If you think there are situations that the "check for space" situation would handle poorly for a goal of proper vote counting, include a test case that illustrates the undesirable behavior (write your test to pass what `clean_votes` actually does, but include a comment about why the result is undesirable.) In general, pay particular attention to the set of strings and vote lists that you include in your test lists. We'll be looking to see how well you explore the space of names and vote lists when grading this question.

Even with removing the single-name votes, people are still concerned that there might be weird issues in the votes. Given prior trends in the district where the votes have been cast, there are expectations on what percentage of the vote specific candidates might get (within a margin of error). We'll write a program to check whether a candidate's votes are within such an expected range.

**Task 9:** In `hw6_code.py`, write a function `check_percent` that takes the name of a candidate, a list of votes, an expected percentage (decimal between 0.0-1.0, inclusive), and an error tolerance (decimal). The function returns one of "higher", "in-range", or "lower". It returns "in-range" if the percentage of votes that the candidate received is within the error tolerance (inclusive) of the expected percentage. Otherwise, "higher" or "lower" is returned based on where the actual percentage lands relative to the error tolerance. For example, if the expected percentage is 0.4 and the error tolerance is 0.03, the function would return `"in-range"` if and only if the candidate got between 0.37 and 0.43 fraction of the vote.

*Hint: This is an excellent problem on which to practice planning. We're not having you develop the plan explicitly, but we strongly suggest that you develop one on paper.*

This task does a statistical, computational spot-check based on expected results. Another option is to have a human-led spot-check on election results.

**Task 10:** One of the electronic voting best-practices that VerifiedVoting recommends is a Risk-Limiting Audit (RLA). In an RLA, people take a random sample (subset) of the votes that were cast and count the votes. They check this work against the answer a computer returned on this sample. If the people get a different answer than the computer, that indicates an error with the computer-based counting that is cheaper to detect than a manual recount. Rhode Island conducted a statewide RLA in June 2020!

When doing an RLA, care must be taken that the random sample is statistically sound. We'll explore the idea of taking a sample here.

Write the following two functions, which try to sample one third of a given list:

- `sample_third` that takes in a list of `Booleans` (yes/no votes) and returns the first 1/3 of the list. *Hint: there are a few ways to approach the problem, but [list slicing](https://docs.python.org/3/tutorial/introduction.html#lists) is probably the most straightforward. Slicing is described in more detail for [strings](https://docs.python.org/3/tutorial/introduction.html#text), but the same principles apply for lists (using item indices instead of character positions). Slice indices need to be `int`s: if you get an error related to this, you can convert a number to an int using `int()`, e.g. `int(6/3)` will be `2`.*
- `sample_every_3` that takes in a list of `Booleans` and returns every 3rd element of the list, starting with index 0 (so for a 9-element list, this function would return the elements at indices 0, 3, and 6). *Hint: you might want to define a variable that helps you keep track of the position in the list as you're looping through it. To check if a number is divisible by another number, you can take the remainder using the `%` (modulo) operator: `8 % 4 = 0`, `9 % 4 = 1`*

You can assume that the length of the input lists is a multiple of 3.

**Task 11:** When testing `sample_third` and `sample_every_3`, one thing we might check is that the samples are representative of the population, that is, the fraction of yes-votes is approximately the same in the input list and the result. In class, we learned that `pytest` is fairly powerful in that it allows us to run any Boolean expression as a test. Come up with a Boolean expression that evaluates to true if and only if the difference between the fraction of yes-votes (`True` values) in the input list and the fraction of yes-votes in the output list is less than 0.1. Use this expression in the following test functions:
- `test_sample_third_representative`, which tests the expression for some input list on the `sample_third` function. You will have to play around with input lists here to make sure your tests pass. In a comment at the bottom of this function, give an example of an input list where the test did not pass.
- `test_sample_every_3_representative`, which does the same thing for `sample_every_3`. You might have to use a different input list to make this test pass. In a comment at the bottom of this function, give an example of an input list where the test did not pass.

**Task 12:** Often, votes come in district-by-district, so voting results will start with all of the votes from district A, then all of the votes from district B, and so on. In a comment under your code for Task 10, answer these questions:
- Which function of `sample_third` and `sample_every_3` would you choose to help ensure a fair sample?
- What advantages does random sampling have over either the `sample_third` method or the `sample_every_3` method?
- Besides statistical soundness of sampling, what other technical challenges do you think RLA poses?

### Part 4: Electronic voting access

In some of the questions above, you’ve thought about how to write code that might increase trust in electronic voting systems through data cleaning, statistical checks, and testing. However, this is not the whole story. Please submit your answers to the following questions in a pdf called `hw6_src.pdf`.

**Task 13:** Read the executive summary from [this report](https://www.brookings.edu/articles/why-the-federal-government-needs-to-step-up-their-efforts-to-close-the-rural-broadband-divide/) by Brookings about broadband access.

**Task 14:** After reading the article, do you think that the issues VerifiedVoting.org focuses on are sufficient to address concerns about access? Why or why not?

**Task 15:** In what ways might this inequity in broadband access compound existing inequalities? Give one or two specific examples.

## Check Block (Autograder Compatibility)

- **Make sure that your inputs for each function are in the order that they are mentioned in the directions**
- Paste the following code at the end of your `hw6_code.py` file and run the code. If `All required methods exist!` prints, you're good to go! If `One of the required methods is missing or named incorrectly` prints, you are either missing a method, or have named one incorrectly.

try:
    assert "name_matches" in dir()
    assert "any_votes_for" in dir()
    assert "count_votes_for" in dir()
    assert "got_more_votes" in dir()
    assert "record_vote" in dir()
    assert "clean_votes" in dir()
    assert "check_percent" in dir()
    assert "sample_third" in dir()
    assert "sample_every_3" in dir()
    print("All required functions exist!")
except:
    print("At least one of the required functions is missing or named incorrectly")

## Double Check You Have Completed All Tasks!

Remember to submit all of your work on Gradescope! The code files you should be submitting are:

:::spoiler `hw6_code.py`
**Tasks to be submitted in `hw6_code.py`:**

**Part 1**
* Task 1: ```name_matches``` function
* Task 2: ```any_votes_for``` function
* Task 3: ```count_votes_for``` function
* Task 4: ```got_more_votes``` function

**Part 2**
* Task 5: ```record_vote``` function

**Part 3**

* Task 7: ```clean_votes``` function
* Task 9: ```check_percent``` function
* Task 10: `sample_third` and `sample_every_3` functions
* Task 12: comment with answers
:::

:::spoiler `test_hw6.py`
**Tasks to be submitted in `test_hw6.py`:**

* Task 1: ```test_name_matches``` function
* Task 2: ```test_any_votes_for``` function
* Task 3: ```test_count_votes_for``` function
* Task 4: ```test_got_more_votes``` function

**Part 2**
* Task 5: ```test_record_vote``` function

**Part 3**
* Task 8: ```test_clean_votes``` function
* Task 9: ```test_check_percent``` function
* Task 10: `test_sample_third` and `test_sample_every_3` functions
* Task 11: `test_sample_third_representative` and `test_sample_every_3_representative` functions
:::

:::spoiler `hw6_src.pdf`
**Tasks to be submitted in `hw6_src.pdf`:**

**Part 4**
* Answers to tasks 14 and 15
:::

## Theme Song
[Axel F](https://www.youtube.com/watch?v=k85mRPqvMbE) by Crazy Frog

------
> Brown University CSCI 0111 (Spring 2024)

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