Lecture I - Introduction

Programming with Python

Dr. Tobias Vlćek

Kühne Logistics University Hamburg - Fall 2026

About this Course

About me

Field: Optimizing and simulating complex systems
Languages: of choice: Julia, Python and Rust
Interest: Modeling, Simulations, Machine Learning
Teaching: OR, Algorithms, and Programming
Contact: vlcek@beyondsimulations.com

I really appreciate active participation and interaction!

Course Outline

Part I: Introduction to Programming with Python
Part II: Data Science Tools with Python
Part III: Programming Projects

Materials live in the KLU portal and are hosted at python.tobiasvlcek.com.

Passing the Course

Pass/fail course, 100 points in total
5 in-class checkpoints × 12 points = 60 points
Final project + presentation = 40 points
You pass with 60 points and 75% attendance
No make-ups for missed checkpoints, but the point math absorbs one miss
Your project is done in pairs; solo works if the numbers don’t come out even

Checkpoints

Short, supervised exercises at the start of some sessions
Solved in the browser, just like our lab notebooks
~6 small tasks each: write code, trace code, fix a bug, MCQs
At the end you download your .py file and upload it to Moodle
Session II has an ungraded 15-minute practice run (Checkpoint 0) before the lab

The weekly lab exercises rehearse exactly this routine. Do them, and the checkpoints will feel familiar.

How a session works

Lecture first: new concepts, with short exercises on your phone or laptop
Then a break
Then the lab: the episode’s notebook, in class, in your browser, with help in the room
Done early? You’re free to go. Not finished when the session ends? Keep the tab open on your laptop and finish at home

How to use AI

We base our assessment on the KLU classification:
- Level 1: Pause: Use of AI defined by the educator
Part I (Sessions I–V) is AI-free: no Claude, ChatGPT, Mistral & Co.
Your sanctioned helper is the course chatbot on the learning website
It gives hints, not solutions, and guides your problem-solving
AI tools are introduced (and then allowed) in Part II, from Session VI on

Learning the basics without AI first is what lets you judge AI output later.

How to use the Chatbot

Just click the chatbot bubble on the website
The chat will open and you can ask your questions
It is programmed by us and uses Mistral AI as backend
Ask your question as specific as possible
This ensures enough context for the model
We can see aggregated logs, but cannot identify you
Please don’t provide personal information

No setup needed today

Everything in Part I runs in the browser: nothing to install
The lab notebooks and exercises run on marimo: click a link, start coding
Before Session X you install Python (via uv) and the Zed editor on your own laptop, with our guides; Session X then runs on your machine
Until then: a laptop, a browser, and one free account (coming up) is all you need

How a notebook works

A notebook is a page of cells; each cell holds a few lines of code
Run a cell: click into it and press Cmd/Ctrl+Enter (or the ▶ button at its edge). The output appears right below it
Change a cell and run it again: every cell that depends on it updates by itself
A cell shows the value of its last line. An assignment like x = 5 shows nothing, so the check under each exercise echoes your result next to the verdict
Save your work: the notebook menu (top right) → Download → Download Python code. The tab remembers you until you close it; the download is forever

One account, today: GitHub

Open github.com → Sign up. This takes five minutes, and we do it right now in class
Use an e-mail you’ll still read next year; your KLU address works well
Pick a username you’d be happy to show a future employer in case you might continue programming in the future
Already have one? Great, you’re done

Why now? From Session VI you get Zed’s paid editor plan for free as a student, and Zed only accepts GitHub accounts that are at least 30 days old. In Session X your project lives on GitHub. Nothing else to install until Session IX.

Episode 1: The Founding

A New Venture

This semester you are founding a campus food-delivery startup. Today it gets a name, a menu, and its first revenue calculation.

(Your co-founder Tobi has already spent the marketing budget on stickers.)

Variables & Types

What is a program?

A program is a list of instructions the computer follows
It runs top to bottom, one line at a time
Writing a program is writing that list, in a language the computer understands

Today your startup’s first program does three small things: record the founding data, do one calculation, and print a summary.

Printing output with `print()`

print() is a function: you hand it something, it shows it on screen.

# The line starting with # is a comment. Python ignores it
print("Welcome to your food-delivery startup!")
print("Stickers bought:", 1200)   # commas print several things, a space between

Welcome to your food-delivery startup!
Stickers bought: 1200

Variables: named values

A variable is a name that points to a value
Create one with =: name on the left, value on the right
You don’t declare a type; Python figures it out from the value

company_founded = 2026        # store a whole number under a name
print(company_founded)

The founding data

Store the facts of the new company, then use them by name:

company_founded = 2026
first_employee = "Tobi"       # co-founder, but he put himself on the payroll first
sticker_budget = 300          # what's left after Tobi's spending spree

print(first_employee)
print(sticker_budget)

Tobi
300

Naming rules

Must start with a letter or an underscore _
Can contain letters, numbers and underscores
Case-sensitive: budget and Budget are two different names
Cannot be a reserved word (for, if, def, …)
Good names are short and meaningful for humans

Question (we solve this together, out loud): Which of these are valid variable names?
sticker_budget, 1st_employee, firstEmployee, company-name, _tobi

Four basic types

Every value has a type, which decides what you can do with the value:

str: text, in quotes ("Tobi", "Falafel Wrap")
int: whole numbers (2026, 300)
float: decimal numbers (9.99, 0.15)
bool: truth values (True, False)

Checking a type with `type()`

type() tells you the type of any value, and it’s priceless when a bug surprises you:

print(type(2026))       # int
print(type("Tobi"))    # str
print(type(9.99))       # float

<class 'int'>
<class 'str'>
<class 'float'>

Predict: quotes around a number

Tobi typed the price with quotes. What does this print?

print(type("9.99"))

a) <class 'float'> b) <class 'int'> c) <class 'str'>

Predict first. Pick a letter, then I reveal the answer.

Answer: `type("9.99")`

c) str: the quotes make it text, however numeric it looks. Tobi’s “price” can’t be multiplied until it is converted to a number.

print(type("9.99"))

<class 'str'>

Your turn — 10 minutes

Open the exercise (scan the QR or type the link):

python.tobiasvlcek.com/notebooks/ex_01_a/

First predict what happens, then run it.

Numbers & Arithmetic

Tobi’s 9.99 theory

Tobi’s grand plan: sell everything for 9.99. To see whether that survives contact with arithmetic, we need Python’s operators.

# margin = price - cost
print(9.99 - 7.40)

2.59

Arithmetic operators

print(9.99 + 1.50)   # addition
print(9.99 - 7.40)   # subtraction
print(9.99 * 3)      # multiplication
print(300 / 8)       # division, always gives a float

`//` and `%`: how many fit, what’s left

// floor division: how many whole times something fits
% modulo: the remainder left over

# The 300 EUR budget, boxes at 7 EUR each
print(300 // 7)      # whole boxes we can buy
print(300 % 7)       # EUR left over
print(10 // 2.5)     # 4.0: floor division on floats floors, but returns a float

42
6
4.0

Precedence: like on paper

* and / happen before + and -. Parentheses override that.

print(2 + 3 * 4)     # 14, not 20
print((2 + 3) * 4)   # 20

14
20

Predict: the sticker budget

Tobi buys 12 boxes at 25 EUR from the 300 EUR budget. What prints?

print(300 - 12 * 25)

a) 0 b) 7200 c) Error

Predict first. Pick a letter, then I reveal the answer.

Answer: `300 - 12 * 25`

a) 0: 12 * 25 = 300 happens first, so the budget is wiped out. Reading left to right would give 7200, but Python follows precedence, not reading order.

print(300 - 12 * 25)

Whole numbers vs decimals

int + int stays an int; / always produces a float
Mixing an int and a float gives a float
Money is decimals, so margins are floats

margin = 9.99 - 7.40
print(margin)
print(type(margin))

2.59
<class 'float'>

`round()`: clean money

Division can leave a long tail of decimals. round(value, 2) keeps two. Cents.

# Split a 10 EUR order three ways
print(10 / 3)              # 3.3333333333333335, ugly
print(round(10 / 3, 2))    # 3.33, a proper amount

3.3333333333333335
3.33

Your turn — 10 minutes

Open the exercise (scan the QR or type the link):

python.tobiasvlcek.com/notebooks/ex_01_b/

First predict what happens, then run it.

Strings & f-strings

The first receipt line

A string is text in quotes. Single or double quotes both work, just be consistent.

item = "Miso Ramen"
print(item)
print('Tobi shouts "9.99!"')   # mix quotes to include a quote inside

Miso Ramen
Tobi shouts "9.99!"

Concatenation, and why it hurts

You can glue strings with +, but numbers must be converted first, and it gets clumsy fast:

qty = 2
item = "Miso Ramen"
total = 23.00
print(str(qty) + "x " + item + ": " + str(total) + " EUR")

2x Miso Ramen: 23.0 EUR

(str(...) turns a value into text, which is clumsy. We’re about to see the better way.) Forget one str() and Python raises a TypeError.

f-strings: the clean way

Put an f before the quote and write values in { }, and Python fills them in:

qty = 2
item = "Miso Ramen"
total = 23.00
print(f"{qty}x {item}: {total} EUR")

2x Miso Ramen: 23.0 EUR

No str(), no +. Just the sentence you want.

Formatting money with `:.2f`

Inside the braces, :.2f forces two decimals, exactly what a receipt needs:

total = 23.00
print(f"{total} EUR")          # 23.0 EUR: one decimal, looks broken on a receipt
print(f"{total:.2f} EUR")      # 23.00 EUR, a proper price

23.0 EUR
23.00 EUR

Python stores 23.00 as the number 23.0. Only you know it’s money, and :.2f says so.

Multi-line receipts with `\n`

\n inside a string starts a new line: one string, several lines.

print(f"Falafel Wrap: 6.90 EUR\nPad Thai: 8.90 EUR")

Falafel Wrap: 6.90 EUR
Pad Thai: 8.90 EUR

Predict: braces or no braces?

What does each line print?

print(f"{2 * 3}")
print("2 * 3")

a) 6 and 6 b) 6 and 2 * 3 c) 2 * 3 and 2 * 3

Predict first. Pick a letter, then I reveal the answer.

Answer: `f"{2 * 3}"` vs `"2 * 3"`

b) 6 and 2 * 3: the f-string evaluates what’s in the braces; plain quotes keep the text literal. The f and the { } are what do the work.

print(f"{2 * 3}")
print("2 * 3")

6
2 * 3

Your turn — 10 minutes

Open the exercise (scan the QR or type the link):

python.tobiasvlcek.com/notebooks/ex_01_c/

First predict what happens, then run it.

To the Lab

After the break: the lab

We do it together in class after a short break; whatever’s left, you finish at home
Head to the lab notebook: Episode 1 — The Founding
You’ll name the company, set prices, and put Tobi’s 9.99 theory on trial
It runs entirely in your browser: no setup, just click and code
Didn’t finish the GitHub sign-up in class? Do it tonight, the 30-day clock is ticking

Download your .py before you leave. Closing the tab without downloading loses your work, and downloading is exactly how you hand in the checkpoints.

Wrap-up

Three things to remember

Variables name values, and every value has a type (str, int, float, bool)
Arithmetic follows precedence: * and / before + and -; round(x, 2) for money
f-strings with {value:.2f} turn numbers into clean receipt lines

Next time — Episode 2: the city bans delivery after 22:00, and Tobi suggests “we just deliver yesterday’s orders.” We’ll need conditionals and loops to survive it. Plus a 15-minute practice checkpoint before the lab, ungraded.

Literature

Books to start with

Downey, A. B. (2024). Think Python: How to think like a computer scientist (Third edition). O’Reilly. Link to free online version
Elter, S. (2021). Schrödinger programmiert Python: Das etwas andere Fachbuch (1. Auflage). Rheinwerk Verlag.

Think Python is a great book to start with and is free online. Schrödinger programmiert Python is a playful German-language alternative with lots of examples.

For more, see the literature list of this course.

Lecture I - Introduction

About this Course

About me

Course Outline

Passing the Course

Checkpoints

How a session works

How to use AI

How to use the Chatbot

No setup needed today

How a notebook works

One account, today: GitHub

Episode 1: The Founding

A New Venture

Variables & Types

What is a program?

Printing output with print()

Variables: named values

The founding data

Naming rules

Four basic types

Checking a type with type()

Predict: quotes around a number

Answer: type("9.99")

Your turn — 10 minutes

Numbers & Arithmetic

Tobi’s 9.99 theory

Arithmetic operators

// and %: how many fit, what’s left

Precedence: like on paper

Predict: the sticker budget

Answer: 300 - 12 * 25

Whole numbers vs decimals

round(): clean money

Your turn — 10 minutes

Strings & f-strings

The first receipt line

Concatenation, and why it hurts

f-strings: the clean way

Formatting money with :.2f

Multi-line receipts with \n

Predict: braces or no braces?

Answer: f"{2 * 3}" vs "2 * 3"

Your turn — 10 minutes

To the Lab

After the break: the lab

Wrap-up

Three things to remember

Literature

Books to start with

Printing output with `print()`

Checking a type with `type()`

Answer: `type("9.99")`

`//` and `%`: how many fit, what’s left

Answer: `300 - 12 * 25`

`round()`: clean money

Formatting money with `:.2f`

Multi-line receipts with `\n`

Answer: `f"{2 * 3}"` vs `"2 * 3"`