Hello, Python

What you'll learn

What Python is, how to print text, and how to leave notes for yourself with comments.

Why it matters

Python is used for websites, data analysis, automation and AI. It is famous for being easy to read, which makes it a great first language.

Explanation

A Python program is a list of instructions that runs from top to bottom. The simplest instruction is print(), which shows something on the screen.

print("Hello, world!")

• Text must be wrapped in quotes. Single ' or double " both work.
• print() can show several things, separated by commas: print("Age:", 30).
• A line starting with # is a comment. Python ignores it. Comments are notes for humans.

Example

# This is a comment: Python skips it
print("Hello, world!")
print("My name is", "Asha")
print("2 + 3 =", 2 + 3)

Step-by-step walkthrough

1. The comment line is ignored.
2. print("Hello, world!") shows Hello, world!.
3. The second print has two items. Python puts a space between them: My name is Asha.
4. In the third, 2 + 3 is worked out first, so it shows 2 + 3 = 5.

Try it yourself

Print a sentence about yourself, then print the result of 10 * 4. The first run downloads Python into your browser, so give it a few seconds.

Common mistakes

• Missing quotes around text: print(Hello) looks for a variable called Hello.
• Mismatched quotes: print("Hi') never closes the string.
• Capital P: Print is not print. Python is case-sensitive.
• Forgetting the brackets: print "Hi" is Python 2 style and an error in Python 3.

Quick quiz

Summary

• print() shows output.
• Text goes in quotes; # starts a comment.
• Python runs top to bottom, one line at a time.

Next: storing values in variables.