Strings

Big idea

A string (str) is text: any characters inside quotes. You can join strings, repeat them, and measure them.

The idea

first = "Ada"
last = 'Lovelace'          # single or double quotes — both fine

Joining strings with + is called concatenation:

first = "Ada"
last = "Lovelace"
full = first + " " + last
print(full)
print("ha" * 3)
print(len(full))

output
Ada Lovelace
hahaha
12

• + joins two strings into one.
• * with a number repeats a string.
• len(...) counts the characters — spaces count too.

Watch it

Text and numbers don't mix with +

+ needs both sides to be strings (or both numbers). Mixing them is an error:

level = 5
print("Level " + level)

output
Level 5

The error is TypeError: can only concatenate str (not "int") to str. Fix it with str(level), or by passing them to print separately: print("Level", level). In a few lessons, f-strings will make this effortless.

A number in quotes is text

print(2 + 3)
print("2" + "3")
print("2" * 3)

5
23
222

Long strings

Triple quotes let a string span several lines, keeping the line breaks:

poem = """Roses are red,
Violets are blue,
Python is readable,
And now so are you."""
print(poem)

output
Roses are red,
Violets are blue,
Python is readable,
And now so are you.

Strings can't be changed in place

A string is immutable: once made, its characters can't be edited. Operations like + build a new string. You'll see why this matters in the Strings module.

Think of it like

Letter beads on a string. + ties two strings of beads together; len counts the beads.

Key terms

• String (str) — Text in quotes.
• Concatenation — Joining strings with +.
• len() — The number of characters in a string.
• Immutable — Can't be changed after it's made.