When people say, “I write Python,” they’re usually referring to two different things at once.

The first is the Python language itself - a set of rules that defines how Python code is written.

For example, this is valid Python code:

print("Hello!")

The second is the program that can execute that code.

Your computer doesn’t understand Python by itself. It needs a special program that reads your code line by line and performs the operations you’ve written.

That program is called the Python interpreter.

Which Python Do You Have Installed?

If you open a terminal and run

python --version

or

python3 --version

you’ll see something like

Python 3.14.0

Many people assume that this is Python.

In reality, it’s simply the version of the program that executes Python code.

The Python language itself is defined separately in its official language specification. Different programs can implement that specification.

The most widely used implementation is called CPython.

In fact, when people say Python, they’re almost always referring to CPython.

Other implementations exist (such as PyPy and Jython), but there’s no need to worry about them just yet.

The First Way to Run Python: The REPL

The easiest way to try Python is without creating any files.

Simply run

python

or

python3

in your terminal.

You’ll see a prompt that looks something like this:

>>>

This is called the REPL.

It stands for:

  • Read - read the command you type;
  • Eval - evaluate it;
  • Print - display the result;
  • Loop - wait for the next command.

For example, type:

>>> 2 + 2

Python responds with:

4

Or try:

>>> print("Hello!")

You’ll get:

Hello!

The REPL is a great place to experiment and try things out.

The Second Way: Running a Script

Most Python code is stored in files.

Let’s create a file called

hello.py

and put this inside:

print("Hello, world!")

Now run:

python hello.py

or

python3 hello.py

The output will be:

Hello, world!

This is how most Python programs are executed.

What Does print() Do?

For now, you can think of print() as a command that says:

“Display something to the user.”

For example,

print("I'm learning Python")

prints

I'm learning Python

And

print(100)

prints

100

That’s all you need to know for now.

Later, we’ll take a closer look at functions and learn why print is written this way.

Script or Program?

You’ll often hear the word script.

In practice, it’s just a Python file.

For example:

backup.py

or

calculator.py

There’s nothing magical about the term.

Historically, smaller programs came to be called scripts, and the name stuck.

What We Learned Today

Today we introduced several important ideas:

  • Python is a programming language.
  • To execute Python code, you need a Python interpreter.
  • The most common interpreter implementation is CPython.
  • Python code can be run in two ways:
    • through the REPL (the interactive interpreter);
    • from a Python file (such as hello.py).
  • The print() function displays information on the screen.

Try It Yourself

Create a file called hello.py and experiment with it.

For example:

print("Hello!")
print("My name is Anna")
print(123)
print(2 + 3)

Try changing the text, the numbers, and the expressions.

See how the output changes.

Don’t be afraid to make mistakes - that’s one of the best ways to learn a new programming language.

What’s Next?

Now that we know how to run Python programs, a new question naturally comes up.

Suppose we write:

name = "John"

Where does Python store that value?

And what does the = operator actually mean?

That’s exactly what we’ll explore in the next article: “Variables and Names.”