Assignments > Lab 5: Understanding Package Managers

Windows Linux If you are a Windows or Linux user, skip this section and jump to §1.2 Apt.

Homebrew is a package manager for macOS that simplifies installing software.

Install a package

1. Open a terminal and check whether brew is installed:

   brew

2. If Homebrew is not installed, install it from https://brew.sh/:

   /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

3. Install wget:

   brew install wget

4. Verify:

   wget --version

5. Download a file into your current directory:

   wget https://www.google.com

   If it worked, index.html appears. View it with cat, then remove it with rm.

6. List packages Homebrew manages:

   brew list

Update and remove packages

1. Update Homebrew:

   brew update

2. Uninstall wget:

   brew uninstall wget

3. Confirm it is gone (this should error):

   wget https://www.google.com

4. Reinstall wget:

   brew install wget

5. Confirm it works again, then delete the downloaded index.html.

Mac If you are a Mac user, skip this section (but make sure you completed §1.1 Homebrew).

APT is the package manager used by Debian-based Linux (for example, Ubuntu in WSL).

Install a package

1. Open a terminal in a Debian-based Linux environment (Windows WSL Ubuntu, or Linux a native Linux shell).

2. Update the local package index:

   sudo apt-get update

3. Install curl:

   sudo apt-get install curl

4. Verify:

   curl --version

5. Save the Google homepage:

   curl https://www.google.com > google.html

   If it worked, google.html appears. View it with cat, then remove it with rm.

Update and remove packages

1. Upgrade installed packages:

   sudo apt-get upgrade

2. Remove curl:

   sudo apt-get remove curl

3. Confirm it is gone (this should error):

   curl https://www.google.com > google.html

4. Reinstall curl:

   sudo apt-get install curl

5. Confirm it works again, then delete google.html.

1. Confirm you are on lab05-b (git branch). If not, return to Set up.

2. Check whether Poetry is installed:

   poetry

3. If it is not installed:

   curl -sSL https://install.python-poetry.org | python3 -

   If this fails on a Mac, you may need SSL certificates:

   • Finder → Applications → Python
   • Double-click the Certificates script
   • Run the curl install command again

4. Verify:

   poetry --version

   • If you get a “command not found” error, add Poetry to your PATH (see common fixes online), for example:

     export PATH="$HOME/.local/bin:$PATH"

5. Go to your lab folder and create a project:

   cd class-exercises-fall2026/lab05
   poetry new poetry-demo
   cd poetry-demo

   Your tree should look like:

   class-exercises-fall2026/
     lab05/
       answers.md
       node-demo/
       poetry-demo/

1. Add requests:

   poetry add requests

2. Confirm it appears in pyproject.toml and is installed:

   poetry show

1. Create lab05-experiments.py inside poetry-demo with this starter code:

   import requests
   
   def main():
       print("hello world")
       # user_agent makes it seem like the request is coming from a web browser (versus a bot)
       user_agent = {'User-agent': 'Googlebot/2.1'}
       response = requests.get("https://new.cs.unca.edu/", headers=user_agent)
       print(response.content)
   
   if __name__ == "__main__":
       main()

2. Run it inside Poetry’s environment:

   poetry run python lab05-experiments.py

   You should see HTML from the CS homepage.

3. Run the same file outside the environment:

   python3 lab05-experiments.py

   You should get an error because requests is not installed for system Python.

Build a small crawler that prints every link on https://new.cs.unca.edu/.

1. Install bs4 with Poetry.
2. Update main in lab05-experiments.py so it prints only the URLs of links on that page.

If it works, you should see something like (about 85 links):

https://unca.edu
https://new.unca.edu/admission/apply/
/
https://new.cs.unca.edu/our-mission/
https://new.cs.unca.edu/our-programs/
https://new.cs.unca.edu/computer-systems-major/
...

Hints:

• Article: Extracting all links with BeautifulSoup

• Import:

  from bs4 import BeautifulSoup

• Parse HTML:

  soup = BeautifulSoup(response.content, 'html.parser')

• Use BeautifulSoup helpers to collect links. You may ask Google or ChatGPT: “How do I extract URLs using Beautiful Soup?”

Optional readiness extension (Practice)

After the basic crawler works, choose one:

1. Deduplicate the links while preserving their original order.
2. Count how many links point to each domain using a Python dictionary.
3. Filter the output to include only links whose domain ends in unca.edu.

Write at least two small tests for the transformation logic using a hand-written list of URLs; do not make your tests depend on the live website. In a comment, name the Java collection you would use for the same algorithm and explain why.

1. Remove the packages:

   poetry remove requests
   poetry remove bs4

2. Run again and notice what happens:

   poetry run python lab05-experiments.py

3. Add them back:

   poetry add requests
   poetry add bs4

4. Run again and notice what happens:

   poetry run python lab05-experiments.py

Check your version:

node -v

• If Node is missing, install it (Mac or WSL steps below).
• If your version is less than 18, talk to Sarah.
• If Node is already ≥ 18, skip to §3.2.

Mac Mac

brew install node
node -v

Windows Linux Ubuntu / WSL

apt’s Node package is often outdated, so install nvm, then Node:

sudo apt-get install -y curl
curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.40.1/install.sh | bash

Restart your WSL terminal, then:

nvm install node
node -v

Source: Installing Node on WSL / Mac / Ubuntu

1. Go to the starter folder:

   cd class-exercises-fall2026/lab05/node-demo

   There are already React starter files here; dependencies are not installed yet.

2. Initialize npm:

   npm init -y

3. Confirm package.json was created.

1. Install packages:

   npm install react react-dom vite

2. Confirm node_modules/, package.json, and package-lock.json updated.

3. In package.json, replace the entire "scripts" entry with:

   "scripts": {
       "start": "vite",
       "build": "vite build",
       "serve": "vite preview"
   },

4. From node-demo, start the app:

   npm start

5. Open http://localhost:5173/. You should see Hello world!

1. Stop the Vite process (Control + C).

2. Install Ant Design:

   npm install antd

3. Replace src/App.jsx with:

   import React, { useState } from "react";
   import { Button, Modal } from "antd";
   const App = () => {
       const [isModalOpen, setIsModalOpen] = useState(false);
       const showModal = () => {
           setIsModalOpen(true);
       };
       const handleOk = () => {
           setIsModalOpen(false);
       };
       const handleCancel = () => {
           setIsModalOpen(false);
       };
       return (
           <>
               <Button type="primary" onClick={showModal}>
                   Open Modal
               </Button>
               <Modal
                   title="Basic Modal"
                   open={isModalOpen}
                   onOk={handleOk}
                   onCancel={handleCancel}
               >
                   <img
                       alt="example"
                       src="https://picsum.photos/400/300"
                       width="400"
                       height="300"
                       style={
                           {
                               width: "100%",
                           }
                       }
                   />
                   <p>Some contents...</p>
                   <p>Some contents...</p>
                   <p>Some contents...</p>
               </Modal>
           </>
       );
   };
   export default App;

4. Start again:

   npm start

5. Open http://localhost:5173/. You should see a modal:

   

Building modals from scratch is tedious; design-system packages like Ant Design let you reuse polished components.