Your First Programs

The smallest useful instruction in Python prints text on the screen:

print("Hello, world!")

print is a function: a named action you can invoke. The parentheses hold the arguments — here, the text to show. Text inside quotes is a string; numbers work too, and print can show several things at once:

print(42)
print("Age:", 42)

Comments — notes to humans

Anything after # on a line is ignored by the interpreter. Comments explain why:

# convert minutes to seconds
seconds = minutes * 60

Programs run top to bottom

print("first")
print("second")
print("third")

Always prints in that order. That simple fact is your first mental model of program flow: execution is a sequence.

Try it now

In the practice set that follows this lesson you will print formatted output, do small calculations, and predict what broken programs print. Reading is fine; now you type.