Python: Hello, world!

Learning a new programming language traditionally begins with 'Hello, World!'. It is a simple program that displays a greeting on the screen and introduces the new language — its syntax and structure.

Hello, World!

This tradition is over forty years old, so we're keeping it. In the first lesson, we'll write a program called Hello, World!. In Python, the command for displaying text is print():

print('Hello, World!')

The way print() works: you put the text you want to display inside the parentheses. To let Python know it's text and not something else, wrap it in quotes. Both single and double quotes work — just make sure the opening and closing quote match:

print('Hello, World!')
print("Hello, World!")

According to the Python style guide (PEP 8), single quotes are preferred for strings when there's no apostrophe inside.

Code             Interpreter          Screen
┌──────────┐     ┌─────────────┐     ┌──────────────┐
│ print(…) │ ──→ │   Python    │ ──→ │ Hello, World!│
└──────────┘     └─────────────┘     └──────────────┘

Every character matters

Programming is not just English text. Code consists of commands, and each command must be written in a specific form. Besides letters, the code uses special characters: quotes ' and ", parentheses (), comma ,, exclamation mark !. Each character has its own role. Skip one or use the wrong one, and the program won't run.

Case matters too. If regular text treats Hello and hello as the same word, Python treats them as different. So print, Print, and PRINT are three different things — and only the first one works.

Practice

Learning to code works best when you try things out as you read. You can run Python code line by line in an interactive environment (REPL) — open it here and experiment as you go through the lesson.

Copy the exact code from the instructions into the editor and run it by clicking “Run”.

print('Hello, World!')

Note: if you write heLLo, woRld! instead of Hello, World!, it will be considered different text, because upper and lower case letters are different characters and different registers. In programming, the register almost always matters, so get used to always paying attention to it!