Lecture I - Introduction

Programming with Python

Dr. Tobias Vlćek

Kühne Logistics University Hamburg - Fall 2025

About this Course

About me

• Field: Optimizing and simulating complex systems
• Languages: of choice: Julia, Python and Rust
• Interest: Modelling, 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

Participation

• Prequisite for course Management Science (taught by me)
• Try actively participating in this course
• You will find it much (!) easier to follow later
• Materials will be provided in the KLU portal
• Slides are hosted at beyondsimulations.github.io/Introduction-to-Python

Teaching

• Lecture: Presentation of tools and concepts, based on small examples and code snippets
• Tutorial: Hands-on examples to be solved in groups
• Difficulty: Difficult at first, but gradually easier

Passing the Course

• Pass/fail course
• 75% attendance required for passing the course
• 2 assignments and 1 little project
• You will be given programming exercises to solve
• You can group up (3 students) and work together
• Each student group submits one solution

Solution

• Provide a code solution to the problem (.py files)
• Code files need to be executable
• Detailed explanations of your code should be provided
• Use comments or docstrings in your code
• Provide a general (verbal) introduction to each problem

I’d encourage you to start and submit your solution early

Difficulty of the Course

• We’ll cover the basics of programming (in Python) at first
• This is similar to learning a new foreign language
• First, you have to get used to the language and learn words
• Later, you’ll be able to apply it and see results
• Similar to learning a language: Practice, practice, practice!

What to expect

• Some investment in the beginning to see the return later
• You can ask questions and get support anytime
• After completion, you will be able to read code
• and write your own program using Python
• That’s quite something!

Goals of the Course

• Essential concepts and tools of modern programming
• Automated solutions for recurrent tasks
• Algorithm-based solutions of complex problems
• Usage of AI in a specific context

Python as Language

• Origins: Conceived in late 1980s as a teaching and scripting language
• Simple Syntax: Python’s syntax is straightforward and easy to learn
• Versatility: Used in web development, data analysis, artificial intelligence, and more
• Community Support: A large community of users and extensive documentation

Artificial Intelligence

How to use AI

• We base our assessment on the KLU classification:
  • Level 1: Pause: Use of AI defined by the educator
• You are allowed to use AI (Claude, ChatGPT, Mistral …)
• Use them to support understanding
• A course chatbot is available on the learning website
• It is designed to guide your problem-solving process

But you should not simply use them to replace your learning.

How to use the Chatbot

• Just click the chatbot bubble on the website
• The chat will open an 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

Why learn programming?

Analytics

Research

Visualization

Finance

Logistics

How to learn programming

My Recommendation

1. Be present: Attend the lecture and participate
2. Put in some work: Repeat lecture notes and try to understand the examples yourself
3. Do coding: Run code examples on your own, play around, google, modify, and solve problems on your own

Great resources to start are books and small challenges. You can find a list of book recommendations at the end of the lecture. Small challenges to solve can for example be found on Codewars.

Don’t give up!

• Programming is problem solving, don’t get frustrated!
• Expect to stretch your comfort zone

Learning Path

• The learning path can be quite steep!
• First of all help each other!
• Try to find help in lecture materials and books, the Python documentation, and online (e.g. Google, ChatGPT, StackOverflow, …)
• In case you get frustrated, read the following helpful blog post about the challenges on medium.com
• In case you find errors or typos, please report them via e-mail to me

Setting up Python

Installing an IDE

• In this course, we will use Zed as our IDE
• Download and install it from https://zed.dev/
• It is available for Windows, Mac and Linux
• It is free to use, lightweight and fast
• Has AI support built-in, which we will use later

What is an IDE?

• Integrated Development Environment = application
• It allows you to write, run and debug code scripts
• Other IDEs include for example:
  • PyCharm from JetBrains
  • Visual Studio Code from Microsoft

Installing Python with uv

• We will use uv to install and manage Python versions
• It works on Windows, Mac and Linux
• It helps us to manage packages and virtual environments
• Now, we all go here and install uv and Python

Python on iPads

• Although you can run Python scripts from on your iPad, it is not recommended for the course
• Nonetheless, you could use Pythonista
• It works locally on your iPad and can run most scripts

Not all packages available in Python are available in Pythonista, thus you might need a computer to solve certain problems.

Your first code

Hello, my name is …!

Task: Open the directory you created for the course and create a new file called hello.py with the following code:

# This is a comment in Python
print("Hello, my name is [YOUR NAME HERE]!")

Hello, my name is [YOUR NAME HERE]!

Run it by executing the following command in your terminal:

uv run python hello.py

Hello, World in a Message

Task: Create a new file called message_world.py file. Assign the string "Hello, World!" to a variable called message and print the variable.

• Use the equals sign (=)
• Variable name goes on the left
• Value to be assigned goes on the right

# Here we assign the string "Hello, World!" to variable message and print it
message = "Hello, World!"
print(message)

Hello, World!

Hello, World in Parentheses

We can also mix " and ' in a string, if we are consistent:

# This code works
message = 'I shout "Hello, World!"'
print(message)

I shout "Hello, World!"

# This code does not!
message = 'I shout 'Hello, World!""
print(message)

Try it yourself! What does happen, if you try to run it?

First Errors

SyntaxError: invalid syntax

• The code is not valid Python syntax
• Likely the most common error that you will encounter!
• Happens when you make a mistake, e.g., illegal character, missing a colon, parentheses or quotations
• You can fix this by correcting the code and re-running
• In the lecture you will encounter many more errors!

Program

What is a Program?

• Sequence of instructions telling a computer what to do
• Written in a language the computer can understand
• Basic operations in most languages:
  • Input: Data from keyboard, file, network, sensors, etc.
  • Output: Display data, save it, send over network, etc.
  • Processing: Perform calculations, analyze data, make decisions, find patterns, etc.

Key concepts

• Key concepts in most languages:
  • Variables: Store and manipulate data
  • Conditional execution: Check and execute accordingly
  • Loops: Perform actions repeatedly
  • Functions: Group instructions for reusability

We will cover these concepts in more detail later in the course.

How Python executes code

• Python is an interpreted language
• The source code is executed line by line
• The interpreter checks the syntax and executes the code
• This is in contrast to compiled languages, where the code is compiled into machine code before execution

Hello again, World!

Let’s go back to our first program:

# Our first program
message = "Hello, World!"
print(message)

• Comment: In the first line we define a comment with #
• Variable: In the second we define a variable message
• Function: In the third line we call a function print

Don’t worry!

• Already confused? Don’t worry about it for now!
• We’ll learn more about variables and functions later

Python’s Syntax

The Zen of Python

• Python’s name originally comes from Monty Python
• Style is based on a philosophy called Zen of Python
• Collection of 19 statements with general principles

Task: Try this code in Python:

# Try this code in Python to see the Zen of Python
import this

Variables

• A variable in Python is a name that points to a value
• Created by using the assignment operator =
• Python does not require a declaration of variable types

a = 2 # Variable a assigned the value 2
b = "Time" # Variable b assigned the value "Time"
c = print # Variable c assigned the print function
c(b) # Now we can call the print function with c

Time

But there are certain rules to variable names!

Variable Naming Conventions

• Must start with a letter or underscore _
• Can contain letters, numbers and underscores
• Names are case sensitive, e.g., a and A are different!
• Cannot be a reserved word, e.g., for, if, def, etc
• Good names are short and meaningful for humans!

Question: Which of the following fulfill these conditions?
a, _duration, 1x, time_left, 1_minute, oneWorld, xy4792

Functions

• Functions are named blocks of code
• Can take arguments function([arguments])
• Can return results or None

# Print is such a function
print("Hello, World!") # It takes an argument and prints it to the console
print("Hello","World!", sep=", ") # It can also take multiple arguments

Hello, World!
Hello, World!

We will cover functions in more detail later in the course.

Values and Types

What are Values and Types?

• Value: Fundamental thing that a program manipulates
  • In Python, values are either numbers or strings
• Type: Type of a value
  • Determines what operations can be performed on it
  • type() is a function that returns the type of a value
  • Takes one argument and returns its type as string

Strings

Back to our example of “Hello, World!”

# We define the variable message and assign it the value "Hello, World!"
message = "Hello, World!"

# We save its type in another variable called message_type
message_type = type(message)

# We print the value of our new variable
print(f"{message} is a {message_type}")

Hello, World! is a <class 'str'>

Result: “Hello, World” is a string - in short ‘str’.

But what about the f”?

Formated Strings

• f-strings are strings that start with f
• They contain expressions, e.g., variables, in braces
• Evaluated at run time and inserted into the string

In older code bases, f strings were not available. Here, interpolation could be done as shown below with print() and .format(). But this method is less concise and arguably less readable.

print("{} is a {}".format(message, message_type))

Hello, World! is a <class 'str'>

Specifying Formatted Strings

• We can further specify their format with {<to_print>:<width>.<precision>f}
• width can be a number specifying the output width
• <, ^, > can be used before the width to align the text
• precision can be used to specify the decimals
• .f can be used to format floats

x = "hello"
print(f"{x:<10} has {len(x):>10.2f} characters.")

hello      has       5.00 characters.

Expressions

• Produce a value when evaluated
• Can be used as part of larger expressions or statements
• Statements are expressions that don’t produce a value
• Examples: arithmetic operations, function calls, variables

x = 1 # Statement that assigns the value 3 to x
y = x + 2 # Expression on the right side assigned to a variable y
print(f"Great, the result is {y}")

Great, the result is 3

A step back: What is a String?

• Remember: “Hello, World” is a string - in short ‘str’
• A string is a sequence of characters enclosed in quotes
• Examples: "Hello", 'World', "123", '1World23'

hello = "Hello"
world = 'World!'
print(hello,world,sep=", ") # We can specify the separator with the argument sep

Hello, World!

Strings are immutable, we can’t change characters in them once created.

String Operations

• But we can also do much more with strings!
• String concatenation, indexing, slicing, length, etc.

two_strings = "Hello" + ", " + "World!" # String concatenation
print(two_strings)

Hello, World!

print(two_strings[0]) # Indexing starts at zero!

H

print(len(two_strings)) # With len we can find the length of our string

13

print("--x--"*3) # We can also repeat strings

--x----x----x--

Booleans

• Booleans represent two values: True and False
• Internally they are represented as 1 and 0, respectively
• They are used for logical operations and control flow
• E.g.: if, while, for, elif, `else

x = True
y = False
print(x)
print(type(y))

True
<class 'bool'>

> More on them in our next lecture!

Integers and Floats

• Integers are whole numbers, e.g.: 1, -3, 0 or 100
• Floats are decimal numbers, e.g.: -4.78, 0.1 or 1.23e2
• Bit size is not specified (e.g.: 64 bits) in Python!

x = 1; y = 1.2864e2 # We can separate multiple operations in one line with semicolons
print(f"{x} is of type {type(x)}, {y} is of type {type(y)}")

1 is of type <class 'int'>, 128.64 is of type <class 'float'>

The interpreter will automatically convert booleans to integers to floats when necessary, but not the other way around!

First Functions and Operators

Arithmetic operators

addition = 1 + 2;           print(f"Result: addition is {addition}")
substraction = 1 - 2;       print(f"Result: substraction is {substraction}")
multiplication = 3 * 4;     print(f"Result: multiplication is {multiplication}")
division = 7 / 4;           print(f"Result: division is {division}")
floor_division = 7 // 4;    print(f"Result: floor_division is {floor_division}")
exponentiation = 9 ** 0.5;  print(f"Result: exponentiation is {exponentiation}")
modulo = 10 % 3;            print(f"Result: modulo is {modulo}")

Result: addition is 3
Result: substraction is -1
Result: multiplication is 12
Result: division is 1.75
Result: floor_division is 1
Result: exponentiation is 3.0
Result: modulo is 1

Precedence

• Operators are the same as in most other languages
• Can be combined with each other and variables
• Normal rules of precedence apply

# Operator precedence works as on paper
combined_operation = 2 + 3 * 4
print(f"2 + 3 * 4 = {combined_operation}")

2 + 3 * 4 = 14

# Parentheses change precedence as expected
parentheses_operation = (2 + 3) * 4
print(f"(2 + 3) * 4 = {parentheses_operation}")

(2 + 3) * 4 = 20

The input() Function

• Used to get user input as string from the console
• Syntax: input([userprompt])
• Displays optional prompt and waits for user input

name = input("What's your name? ")
print(f"Hello, {name}!")

The function always returns the input as string!

Input in Action

Task: Solve the following task:

# TODO: Ask the user for their age and print a compliment

Solution

age = int(input("How old are you? "))
print(f"You look great for {age}!")

Type Conversion

Use type conversion for other data types

1. Integer: int(input())
2. Float: float(input())
3. Boolean: bool(input())
4. String: str(input())

# Converting to Integer
age = int(input("Enter your age: "))
next_year = age + 1
print(f"Next year, you'll be {next_year}")

The round() Function

# Hence, we can use the int() function to convert a float into an int
soon_int = 1.789
print(f"{soon_int} converted to {int(soon_int)} of type {type(int(soon_int))}")

1.789 converted to 1 of type <class 'int'>

# We can also use `round()` to round a float to an int
soon_int = 1.789
print(f"{soon_int} converted to {round(soon_int)} of type {type(round(soon_int))}")

1.789 converted to 2 of type <class 'int'>

# Or to a float with a certain number of decimals
no_int = 1.789
print(f"{no_int} converted to {round(no_int,1)} of type {type(round(no_int,1))}")

1.789 converted to 1.8 of type <class 'float'>

Questions?

That’s it for todays lecture!
We now have covered the basics on the Python syntax, variables, and data types.

Literature

Interesting Books to start

• 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. It’s available online for free here. Schrödinger Programmiert Python is a great alternative for German students, as it is a very playful introduction to programming with lots of examples.

For more interesting literature to learn more about Python, take a look at the literature list of this course.