Are Python strings zero-indexed?

Yes. The first character of s is s[0]. Negative indices count from the end, so s[-1] is the last character.

Do string methods change the original string?

No. Strings are immutable, so methods like .upper() and .strip() return a new string. If you want to keep it, assign the result: name = name.strip().

An f-string is a formatted string literal, prefixed with f. Inside braces you can drop variables and expressions directly, e.g. f"Hello, {name}!". Cleaner than concatenation with +.

Python string manipulation

Strings are the most-used data type in real Python programs, and every UK GCSE Computer Science specification lists string handling as a required skill. This unit covers indexing (s[0]), slicing (s[0:3]), len(), the common string methods (.upper(), .lower(), .strip(), .split(), .replace(), .find()), concatenation with +, and f-strings for clean formatted output. Every snippet runs in the browser so learners can try edge cases (empty strings, spaces, mixed case) themselves. Perfect for classroom teaching, GCSE and A Level revision, and independent or home-schooled learners.

What you'll learn

Index individual characters with s[0], s[1], s[-1]
Slice substrings with s[start:end]
Use len(s) to measure a string
Clean input with .strip(), .lower(), .upper()
Split and join strings with .split() and .join()
Format output with f-strings

UK GCSE topic coverage

Strings as sequences
String indexing
String length reasoning
String `+` and `*`
String equality
String methods (case)
String methods (whitespace)
String slicing
Applied strings
Applied strings + selection
String methods (`in`, `.count()`)

Worked example

Validate and format a name from user input

raw = input("Name? ")
name = raw.strip().title()
if len(name) == 0:
    print("You didn't type anything.")
else:
    print(f"Hello, {name}!")

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Lessons in this unit

Full interactive lessons with checked tasks are available to signed-in RunPy users. Unit 1 and a selection of exam-style questions are free with a RunPy account.

Strings as sequences of characters
Positive indexing and boundaries
Negative indexing
Using len() and off-by-one reasoning
Concatenation and string repetition
String comparison and case sensitivity
Normalising text with .lower() and .upper()
Cleaning input with .strip()
Slicing basics: extracting substrings
Left and right slice patterns
GCSE pattern: username creation
GCSE pattern: password validation
Checking which characters are in a string

Frequently asked questions

Are Python strings zero-indexed?: Yes. The first character of s is s[0]. Negative indices count from the end, so s[-1] is the last character.
Do string methods change the original string?: No. Strings are immutable, so methods like .upper() and .strip() return a new string. If you want to keep it, assign the result: name = name.strip().
What's an f-string?: An f-string is a formatted string literal, prefixed with f. Inside braces you can drop variables and expressions directly, e.g. f"Hello, {name}!". Cleaner than concatenation with +.