What is Python?

Talking to a computer

A computer is fast and obedient, but it takes everything literally. It won't guess what you meant. To get it to do something, you give it exact instructions, one after another. A list of instructions like that is a programprogramA set of instructions a computer follows, written in a language it can run..

You can't write those instructions in Amharic or English, because everyday language is full of guesses and shortcuts. Instead you use a programming languageprogramming languageA language with strict rules, designed so that humans can write instructions and computers can follow them exactly.: a language small and strict enough for a computer to follow, but still readable by people. Python is one of them.

Here is a tiny Python program. You don't need to understand it yet. Press Run.

print("Selam! Python is working.")
print("Three macchiatos cost", 3 * 45, "birr.")

Two lines of instructions, two lines of results. The second line even did some arithmetic for you: 3 * 45 means three times forty-five. Try changing 3 to 5 and run it again.

How Python reads your code

Your computer's processor doesn't understand Python directly. Something has to translate. Languages handle this in one of two ways.

Some languages are compiledcompiledTranslated into machine instructions all at once, before the program runs. C and Go work this way.: a tool translates the whole program into machine instructions first, and you run the result later. Python is interpretedinterpretedRead and carried out by another program, the interpreter, one step at a time while it runs.: a program called the Python interpreter reads your code from the top and carries out each line as it gets there. That's why you can change a line and see the effect a second later, with no build step in between.

You can see this line-by-line reading for yourself. The third line below has a typo. Before you run anything, decide what you'll see.

print("one")
print("two")
prnt("three")

one
two
Traceback (most recent call last):
  File "<your code>", line 3, in <module>
    prnt("three")
    ^^^^
NameError: name 'prnt' is not defined. Did you mean: 'print'?

What Python is for

Python is one of the most used programming languages in the world, and it turns up in very different kinds of work.

• Web backends. The code behind websites and apps: logging people in, saving data, answering requests. Frameworks like Django and FastAPI are written for Python.
• AI and machine learning. Most of today's AI tools are trained and served with Python libraries such as PyTorch.
• Data work. Cleaning spreadsheets, analyzing exam results, drawing charts. Analysts use Python where Excel runs out.
• Automation. Small scripts that rename a thousand files, send reminders, or collect prices from a website while you sleep.

The same language, the same basics, used in every one of those places. What you learn in the Shallows carries all the way down.

Why start with Python

Python was designed to be read by people. It uses plain words like if, for, and print instead of symbols, and its rules are few and consistent. Compare these two ways of showing a greeting:

public class Main {
    public static void main(String[] args) {
        System.out.println("Selam");
    }
}

print("Selam")

Both do the same job. The Python version lets you focus on the idea instead of the ceremony around it. That matters when you're starting out: fewer rules to fight means more energy for learning how to think in steps.

What you'll build in this course

This course starts in the Shallows, where you're reading now, and goes down through Currents and Deep Water to Landfall, where Python meets the web.

Along the way you'll build one project that grows with you: Birr Ledger, a personal expense tracker. It starts as a short script that records what you spent on coffee and taxis. Module by module it gets tests, classes, type checking, and concurrent downloads of exchange rates, until it's a real Python package ready to become an API in the FastAPI course.

For now, you only need one thing: the next lesson, where you'll install Python on your own computer.