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Hello World in Python

Index

Python is one of the most popular programming languages. In this guide, we’ll walk through the simplest possible example: printing “Hello, world!”.

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Install Python

Download Python from the official website and install it:

• https://www.python.org/downloads/

Python is cross-platform and works on Windows, Linux, and macOS.

After installation, open a terminal to verify it:

• Windows: PowerShell or Command Prompt
• Linux: Bash
• macOS: Terminal

Run:

python --version
python3 --version
py --version   # Windows only

Depending on your system, you may use python, python3, or py. If Python is installed correctly, the command will print the installed version.

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Say Hello in the Terminal

Start the Python interactive environment:

python

(or python3/py depending on your operating system.)

You will see a prompt like:

>>>

Then type:

print("Hello, world!")

Press Enter, and you will see:

Hello, world!

Explanation:

• print() is a built-in function used to display output
• "Hello, world!" is a string (text)
• Parentheses () are used to pass arguments to the function

Two useful functions in the interactive environment:

help()
quit()

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Save the Script to a File

Instead of typing code interactively, you can save it in a file.

Create a file named helloworld.py:

print("Hello, world!")

Run it in the terminal:

$ python helloworld.py
Hello, world!

Or:

$ python3 helloworld.py
Hello, world!

On Windows:

> py helloworld.py
Hello, world!

Here, python (or python3 / py) is the Python interpreter. It works because the Python executable is included in your system’s PATH, which allows the terminal to locate and run it.

You can inspect PATH using:

• Linux/macOS:

  echo $PATH
  

• Windows (PowerShell):

  $env:PATH
  

• Windows (Command Prompt):

  echo %PATH%
  

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Shebang (Optional)

On Linux and macOS, you can make a script executable by adding a shebang line:

#!/usr/bin/env python3
print("Hello, world!")

Then make the file executable:

chmod +x helloworld.py

Run it directly:

./helloworld.py

(Run this in the same directory as the file.)

Windows will ignore the shebang line but it is usually left in for portability.

What is a shebang?

• #! tells the operating system this is a script
• /usr/bin/env python3 locates the python3 interpreter and runs the script

Notes:

• Works on Linux and macOS
• Not required on Windows
• Requires executable permission (chmod +x)

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File Name Suffix

Python files usually use the .py suffix:

helloworld.py

This is a convention, not a requirement. Python can run files with any name, but using .py is strongly recommended for:

• readability
• editor support
• tooling compatibility

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Summary

You’ve now seen three ways to run Python code:

1. Interactive mode (python)
2. Script file (python helloworld.py)
3. Executable script with shebang (Linux/macOS)

This is the simplest possible Python program—but it’s the starting point for everything else.

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