Printing and Comments

Standard Output (print)

When a program displays text on the screen, we call this standard output. In Python, you use a function called print() — whatever value you put inside the parentheses gets displayed on the screen.

Even the classic "Hello, World!" that opens every beginner's book is just a simple program using print() to show that string.

You can wrap strings in either "..." (double quotes) or '...' (single quotes) — both mean the same thing. Just make sure the opening and closing quotes are the same type.

Numbers don't need quotes.

print("Hello, World!")    # Hello, World!
print('Hi there')         # Hi there

# Numbers don't need quotes
print(123)                # 123

# Separate with commas and they're joined with a space
print("Python", "is fun") # Python is fun

Try these two exercises in the console (if you run them correctly, an explanation will appear).

① Use print() to display Hello, World!.

② Display the message I just started Python.

Comments

Comments are notes you can leave inside your program. Python ignores them at runtime, so they exist only for humans to read.

Writing them takes a bit of effort, but they help other developers understand what your code is doing.

Single-line comments (#)

Write a # (hash), and everything from there to the end of the line becomes a comment.

You can place it at the start of a line or partway through a line, which makes it handy for leaving notes inside your code.

Multi-line comments ("""...""")

When you want an explanation that spans multiple lines, wrap it with """ (three double quotes) on both sides and everything inside is treated as a comment.

Strictly speaking it's a "multi-line string," but if you don't assign it to anything, it effectively behaves the same as a comment.

# This is a single-line comment
print("This runs")   # You can also add comments at the end of a line

"""
You can use this
as a comment
spanning multiple lines
"""

print("This runs too")

Comments can also temporarily disable code

Add a # at the start of a line you don't want to run, and that line gets skipped. This is called commenting out, and it's handy when you're debugging or experimenting.

Try the following in the console on the right.

① Rewrite the line starting with # into any note you like.

② Add a multi-line comment wrapped in """...""".

③ Check that only the print() line runs — neither comment appears on the screen.

Embedding values with f-strings

So far you've only printed fixed strings. In real code, though, you'll often want to mix a variable's value into your text — something like "Hello, {Alice}!" (we'll cover variables on the next page).

That's what f-strings are for. Just add an f in front of the string and write {variable_name}, and the variable's value gets dropped in right there.

name = "Alice"
age = 18

# f-string: put the variable name inside {}
print(f"My name is {name}")           # My name is Alice
print(f"I'm {name}, {age} years old") # I'm Alice, 18 years old

# You can write expressions inside {} too
print(f"Next year I'll be {age + 1}")  # Next year I'll be 19

# For reference: the older .format() style does the same thing
print("My name is {}".format(name))    # My name is Alice

f-strings are available from Python 3.6 onwards and are the current standard way to do this.

The older "...{}...".format(value) style was the standard way to do this, but if you're learning today, just stick with f-strings.

Try printing a self-introduction with an f-string.

① Assign "Alice" to the variable name and 18 to age.

② Use an f-string to display I'm Alice, 18 years old.

In this article you've picked up Python's first essential tools — printing to the screen with print(), writing comments with # and """...""", and embedding variables into strings with f-strings.

With these, you can already write basic programs that assemble values and show them on the screen. In the next article, we'll cover variables — the boxes that hold your values.