Lesson 6: Strings: Text, Quotes, and Length

What you'll learn in this lesson

• What a string is
• Single quotes, double quotes, and when each is handy
• How to join strings together
• How to repeat a string
• How to count a string's length and read one character

What a string is

A string is text: any sequence of characters — letters, digits, spaces, punctuation — wrapped in quotes. "Hello", 'Sam', "I am 9 years old" are all strings. The quotes are what tell Python "this is text, not a name and not a number."

message = "Hello, world!"
print(message)

Output:

Hello, world!

A string can hold digits too: "42" is a string, not a number. That is why Lesson 5's "5" + "3" gave "53": Python treated both values as text. If you need arithmetic, the value must be a number without quotes.

Single quotes or double quotes?

Both work, and they mean exactly the same thing. The trick is picking the kind that does not clash with the text itself:

print('Sam said "Hi!"')
print("It's a sunny day.")

Output:

Sam said "Hi!"
It's a sunny day.

The first line uses single quotes on the outside so the double quotes inside are safe. The second uses double quotes outside so the apostrophe in It's is safe. Choose whichever keeps your text intact; there is no other difference.

Joining and repeating strings

+ joins strings end to end. This is called concatenation:

first = "Hello"
second = "Sam"
print(first + " " + second)

Output:

Hello Sam

Note the " " in the middle: without it, you would get HelloSam, because Python joins exactly what you give it and adds nothing on its own. Spaces, commas, and punctuation are your job.

* repeats a string:

print("Ha! " * 3)

Output:

Ha! Ha! Ha!

That is the same * as multiplication — with text, it means "repeat."

A string and a number do not join. Try it and Python stops with an error:

print("You are " + 9)

TypeError: can only concatenate str (not "int") to str

Python will not guess what you mean. Turn the number into text first with str(): print("You are " + str(9)). Or use a comma, the way Lesson 4 showed: print("You are", 9) prints You are 9.

Length, and reading one character

len() counts how many characters a string has, including spaces:

word = "hello world"
print(len(word))

Output:

11

Count it yourself: h-e-l-l-o (5), one space (6), w-o-r-l-d (11). Spaces count, which is the detail beginners most often miss.

You can also read a single character by its position. Counting starts at 0, not 1 — the first character is position 0:

word = "Sam"
print(word[0])
print(word[1])
print(word[2])

Output:

S
a
m

word[0] is S, word[1] is a, word[2] is m. Asking for a position past the end, like word[3], gives an error — IndexError: string index out of range — because there is no fourth character. Zero-based counting feels strange for a day and then becomes second nature — most popular languages count this way.

The last character is at position len(word) - 1 — one less than the length, because counting starts at 0:

word = "Sam"
print(word[len(word) - 1])

Output:

m

Putting it together: a friendly message

Strings, variables, and joining combine into the kind of line you see in real programs:

name = "Mia"
print("Hello, " + name + "! You are learning Python.")

Output:

Hello, Mia! You are learning Python.

Joining with + is the foundation, and it always works.

Hands-on exercise

1. Store your first name in a variable and print a greeting built with +, like the example above.
2. Print the length of your name with len(). Count by hand and check they match.
3. Print the first and last characters of your name using positions (remember: counting starts at 0 — and the last character is at position len(name) - 1).
4. Try "Boo! " * 5 in the shell and explain the result in one sentence.

Quick quiz

1. What is a string?
2. Why might you choose single quotes instead of double quotes?
3. What does "Hello" + " " + "Sam" produce, and why is the " " needed?
4. What is len("hello world"), and does the space count?
5. In the string "Sam", what is position 0, and what happens if you ask for position 3?

Answer key: 1. Text wrapped in quotes. 2. To let the other kind of quote appear safely inside the text (for example, an apostrophe inside double quotes). 3. Hello Sam — without the space string you would get HelloSam. 4. 11, and yes, the space counts as a character. 5. Position 0 is S; position 3 is an error, because there is no fourth character.

Key takeaways

• A string is text in quotes; "42" is text, not a number.
• Single and double quotes mean the same thing — pick the kind that does not clash with your text.
• + joins strings; * repeats them; Python adds no spaces for you.
• len() counts characters, including spaces.
• Positions start at 0: word[0] is the first character.

Next lesson: Talking to Your Program: input().

Slides

Work through the slides with Helio's narration, or download them:

Open the slidesDownload PowerPointDownload PDF

Try it yourself

Run the lesson's example with real Python, right in your browser (Python loads from the internet, so you need to be online).

Open the demo

Practice file

Download lesson06-practice.pyDownload the solution

# Lesson 6: Strings — Text, Quotes, Length
# WHAT TO DO: A string is text inside quotes. This program stores a
# name and should build a greeting by joining strings with +.
# Fill in line 11: replace the placeholder word with the variable name
# (no quotes around it), so the greeting uses the stored name.
# HINT: Joining "Hello, " and the name gives "Hello, Sam". A variable
# name on its own means "use the value stored under that name".
# Run with F5 in IDLE. You are done when you change `name` to your own name, run again, and the greeting changes too.

name = "Sam"
greeting = "Hello, " + "TODO"  # <-- CHANGE THIS LINE: use the name variable
print(greeting)
print(len(name))

Save the file as lesson06-practice.py and run it with F5 in IDLE. On a Mac, if F5 does nothing, use Run, then Run Module, from the menu.

Check yourself

Five quick questions on this lesson. Take the Lesson 6 quiz