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Python Strings Introduction

A string is a piece of text, like a necklace of letter beads. You can look at each bead by its position and count how many there are.

In this page:

  1. Creating Strings
  2. Accessing Characters
  3. String Length
  4. Multiline Strings
  5. Immutability of Strings
Syntax
python 
variable = "text"
variable = 'text'
variable = """multi-line
text"""

Creating Strings

A string is an ordered sequence of characters, and Python lets you create one with single quotes, double quotes, or triple quotes — all three produce the exact same str type, so the choice comes down to convenience, like avoiding escaping an apostrophe.

Example: Creating Strings

python 
s1 = 'single'
s2 = "double"
s3 = """triple"""
print(type(s1), type(s2), type(s3))  # all three are the same str type

Accessing Characters

Square-bracket indexing, like text[0], retrieves a single character at that zero-based position; Python also supports negative indices, so text[-1] retrieves the last character without needing to know the string's length first.

Example: Accessing Characters

python 
text = "Python"
print(text[0])  # first character, index 0
print(text[-1])  # last character, negative indexing counts from the end

String Length

len(text) returns the total character count of a string, including spaces and punctuation — a value you'll reach for constantly when validating input length or iterating with an index-based loop.

Example: String Length

python 
text = "Hello, World!"
print(len(text))

Multiline Strings

Triple-quoted strings ("""...""") can span multiple lines exactly as typed, preserving line breaks — the standard way to embed a block of formatted text, a docstring, or a multi-line message without manual \n characters.

Example: Multiline Strings

python 
message = """Line one
Line two
Line three"""  # triple quotes preserve the line breaks as typed
print(message)

Immutability of Strings

Once created, a Python string can never be modified in place — operations like .upper() or .replace() don't change the original string, they return a brand-new one, leaving the original untouched in memory.

Example: Immutability of Strings

python 
text = "hello"
upper_text = text.upper()  # returns a new string, doesn't modify text
print(text)  # still lowercase
print(upper_text)
Related Topics

Python f-strings · Python Format Strings · Python Closures · Python Scope & Lifetime

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Common Mistakes
  1. Trying to change a character in place with s[0] = "J", which raises TypeError because strings are immutable; build a new string instead.
  2. Using an index equal to the length, as in s[len(s)], which raises IndexError since valid indexes end at len(s) - 1.
  3. Forgetting that len() counts characters and spaces, so len("hi there") is 8, not 2.
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