GCSE Computer Science

Python strings — GCSE Computer Science

What is a string?

A string is a sequence of characters. Every character has a position — an index — starting from zero. That means strings and lists share a fundamental property: both are ordered sequences that you can access by index. The skills transfer directly.

In GCSE Computer Science, string manipulation questions test whether students can work with text programmatically — extracting parts of a string, measuring its length, combining strings together. These operations appear on every exam board.

Length and indexing

name = "Python"
print(len(name))   # 6
print(name[0])     # P
print(name[5])     # n
print(name[-1])    # n  (last character)

len() returns the number of characters. Indexing works the same way as lists — zero-based, left to right. Negative indices count from the end: name[-1] is the last character, name[-2] is the second to last.

Substrings

word = "Computer"
print(word[0:4])   # Comp
print(word[4:])    # uter
print(word[:3])    # Com

A substring is a slice of a string. word[0:4] gives you characters at index 0, 1, 2, and 3 — the end index is excluded. This is consistent with how range() works: the stop value is never included. That pattern appears throughout Python.

Concatenation and string methods

first = "Python"
last = "Coach"
full = first + " " + last
print(full)           # Python Coach
print(full.upper())   # PYTHON COACH
print(full.lower())   # python coach

Concatenation joins strings with +. String methods like .upper() and .lower() return a new string — they don't change the original. GCSE exams also test .strip() (removes whitespace) and occasionally .replace().

What examiners actually test

String questions fall into three categories: length and indexing (what does name[2] return?), slicing (what does word[1:4] return?), and concatenation or method application. The slice end-index being excluded is the most consistently tested edge case — word[0:4] gives four characters, not five.