Polars and array processing lab

ssh

Set up your ssh keys according to ssh configuration

git and forgejo

Introduce yourself to git

Where are you working? Make a directory structure.

Tell git your full name and email

git config --global user.name "Your Name"
git config --global user.email "you@example.com"

Check if git knows your full name and email

git config --get user.name
git config --get user.email

Make a git repository

Only one member of your team should do this!

This is my directory structure. You may choose your own

cd
pwd
cd projects/auc/courses/ml/repos
mkdir trial-repo
cd trial-repo

Now make this a git repo
```
git init
```

Use your code editor (Spyder, vim, Visual Studio, Emacs) to edit a python file

def factorial(n):
    if n == 0:
        return 1
    else:
        return n * factorial(n - 1)

Save it to factorial.py
Check the git status and note the branch name
```
git status
```
Add it to the git index
```
git add factorial.py
```

Commit it and check the log

git commit -m "Add factorial file"
git log

Make a remote repo on Forgejo

Use the + at to top right to make a new repo.
Give it a sensible name, e.g. the same as the repo on your laptop trial-repo
Under the Advanced settings check that the name of the Default branch matches that on your laptop.
Click Create repository
There are three headers
- Under "Clone this repository" you will see HTTPS highlighted. Click on SSH beside so that is highlighted.
- You can ignore "Creating a new repository on the command line". We have done most of that.
- Under "Pushing an existing repository from the command line" you will see two commands. Copy paste these into your command line where you made your repo on your laptop.
- Reload the Forgejo page. You should see your Python file.

Get your partner on board

On the Forgejo page, click Settings (near the top right)
On the left click Collaborators
In the Search users.. box, type your partner's Forgejo userid.
Click "Add collaborator"
You should see a line with their name. On the right should be Write. This means that they can write to (and read from) the repo.
Now click on the repository name trial-repo near the top left.
Your partner(s) should go to this page too. They should see near the top on a red background either HTTPS or SSH. They should click on SSH so that it is red. Then copy the URL beside it. It should be something like
```
ssh://forgejo@git.auc-computing.nl/bon/trisl-repo.git
```
Now your partners(s) should cd to the place in their directory structure where they want to keep their repos for the ML course.
They shold now clone the repo with this command on the command line
```
git clone ssh://forgejo@git.auc-computing.nl/bon/trisl-repo.git
```
The can cd to that directory, see the Python file and check the git log
```
cd trial-repo
ls -l
git log
```

Collaborate!

Now you and your partner(s) should take turns editing the file(s) in the repo.
After each edit
1. add
2. commit
3. push to Forgejo using
```
git push
```

Markdown

Markdown is a "simple and easy-to-use markup language you can use to format virtually any document."
- markdown-cheat-sheet.md
We will use it to write our reports.
In your repo, make a markdown file called README.md and push it. Notice how Forgejo formats it beautifully.

Chapter 2 Lab: Introduction to Python

With your partner, work through the Lab on Polars and Array Processing

Exploring data

Section 2.4 of the ISLP book has three exercises 8, 9 & 10, each of which explores a data set, step by step. Carry out each of these steps but using Polars instead of Numpy and Pandas.

A zip file containing all data sets for ISLP can be found at datasets

When loading a .csv file using pl.read_csv be sure to give the full path name of the file or make sure that Python is working in the directory where the data file is found.

etc

Jotter 2026-09-03