Practice String in CS Thinking

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

Worksheet PDF Free Answer-key PDF Family

Quick Recap

A data type that represents a sequence of characters (text), enclosed in quotation marks. Strings support operations like concatenation (joining), slicing (extracting substrings), searching, and comparison, and can contain letters, digits, spaces, and special characters.

A string is text in code — anything between quotes. Numbers inside quotes are text too: '42' is a string, not a number.

Showing a random 20 of 50 problems.

Example 1

hard
Given `s = "abcdef"`, what is `s[::-1][1:4]`?

Example 2

medium
What does `"abc".replace("b", "X")` produce?

Example 3

easy
How many characters are in `"a b"` (with the space)?

Example 4

challenge
Build the substring of `"computer"` from index 2 up to but not including the last character. What is it?

Example 5

easy
What is the length of `"science"`?

Example 6

easy
Repeat a string: what is `"ab" * 3`?

Example 7

hard
Write a one-liner check: is `"level"` a palindrome?

Example 8

challenge
Check if `"racecar"` is a palindrome by comparing it to its reverse. Result?

Example 9

hard
Given `s = "AbCdE"`, count uppercase letters using a comprehension.

Example 10

medium
Given `s = "abcde"`, what is `s[1:4]`?

Example 11

easy
Given `s = "data"`, what is `s[-1]` (last character)?

Example 12

easy
What is the length of `"world"`?

Example 13

easy
Given `s = "cat"`, what is `s[2]`?

Example 14

medium
Given `s = "abc"`, in Python `s[0] = "z"` raises an error. Why?

Example 15

hard
Given `s = "abcabc"`, count occurrences of substring 'bc'.

Example 16

easy
Given `s = "sun"`, what is `s[-1]`?

Example 17

medium
What is the result of concatenating 'Score: ' + STRING(95) + '%'?

Example 18

medium
Build a greeting: `name = "Sam"`; produce `"Hello, Sam!"` using concatenation.

Example 19

challenge
Given `s = "abcdefg"`, what does `s[1:6:2]` produce?

Example 20

medium
Strip whitespace: `" hi ".strip()` returns?
← Back to String Worked Examples