Reverse a string
Return the characters of the string in reverse order.
Palindrome check
Return True if the string reads the same forwards and backwards (ignoring case and non-alphanumeric).
Count vowels
Count the number of vowels (a, e, i, o, u) in a string (case-insensitive).
Title case converter
Return the string with each word capitalised.
Anagram check
Return True if two strings are anagrams of each other.
Strip and Collapse Whitespace
Write a function that strips leading/trailing whitespace and collapses inner runs of whitespace to single spaces.
Snake case to camel case
Implement a function that converts snake_case strings to camelCase.
Camel case to snake case
Write a function that converts camelCase input to snake_case while handling acronyms and numbers correctly.
Remove punctuation
Write a function that removes all ASCII punctuation characters from a string.
Is pangram
Write a function that determines whether a given string is a pangram, ignoring case and non-letter characters.
Caesar Cipher Shift
Implement a function to apply a Caesar cipher shift to a string, preserving case and ignoring non-letters.
Repeat each character n times
Given a string s and an integer n, return a new string where each character of s is repeated n times consecutively.
Longest word in a sentence
Write a function that returns the longest word from a sentence, with first-occurrence tie-breaking.
Replace vowels with stars
Write a function that replaces every vowel in a given string with an asterisk.
Is isogram
Implement a function that determines whether a string is an isogram (no repeated letters, case-insensitive).
Extract Digits Only
Given a string that may contain letters, symbols, and whitespace, extract all digits in order and return them as an integer.
Kebab Case a Phrase
Implement a function that converts a phrase into lowercase kebab-case, handling spaces, punctuation, and camelCase.
Normalize quotes
Replace all typographic quote characters with straight ASCII quotes.
Find all indexes of a substring
Write a function that returns a list of all starting indexes where a substring appears in a string, including overlapping occurrences.
Remove Consecutive Duplicate Letters
Implement a function that removes consecutive duplicate letters from a string, keeping only one occurrence of each run.
Interleave Two Strings
Given two strings s1 and s2, return a new string that interleaves them character by character, starting with s1.
Is rotation of another string
Write a function to determine if one string is a rotation of another string.
Sort characters alphabetically
Sort all characters in a string alphabetically and return the sorted string.
Initials from a Full Name
Return the uppercase initials of each word in a given full name.
Count words in a sentence
Implement a function to count words in a sentence, ignoring extra whitespace and handling empty strings.
Center a string in a width
Write a function that centers a string within a specified width by adding spaces on both sides.
Caesar Cipher Shift
Write a function that shifts letters in a string by a given amount, preserving case and ignoring non-letters.
Reverse Words in a Sentence
Reverse the order of words in a sentence while preserving single spaces between words.
Count consonants
Write a function that counts the number of consonant letters in a string.
Is pangram?
Implement is_pangram(s) to return True if the string contains every letter from 'a' to 'z' at least once, ignoring case and non-alphabetic characters.
Remove Duplicates from String
Given a string, return a new string with each character that repeats consecutively reduced to a single occurrence.
Longest Word Finder
Write a function that extracts alphabetic words from a string and returns the longest one, with ties broken by earliest position.
Abbreviate Name
Create a function that takes a full name and returns an abbreviated version with initials and the last name.
Mask email address
Given an email address, return a masked version that hides everything but the first and last character of the local part and the domain.
Extract digits from string
Write a function that extracts all digit characters from a given string, preserving their original order.
Replace Spaces with Dashes
Write a function that replaces every space in a string with a dash.
Capitalize First Letter
Write a function that capitalizes the first letter of each word in a string.
Snake case converter
Implement a function that converts a string to snake_case according to given rules.
Camel Case Converter
Write a function that converts a space-separated phrase into lower camelCase.
Kebab Case Converter
Implement a function that converts any string to kebab-case, handling spaces, underscores, camelCase, and punctuation.
Count Syllables (Simple)
Count syllables in a word by counting groups of consecutive vowels (a, e, i, o, u).
Is isogram?
Write a function that checks whether a given word is an isogram, ignoring letter case and only considering alphabetic characters.
Rotate String Right
Implement a function that rotates a given string to the right by a specified number of positions, handling shifts larger than the string length.
Compress Consecutive Chars
Write a function that compresses a string by replacing runs of identical characters with the character followed by the count.
Expand compressed string
Implement a function that expands run-length encoded strings (e.g., 'a3b2' → 'aaabb').
Find substring index
Implement a function that returns the starting index of the first occurrence of a substring using only basic string indexing and slicing.
Count Substrings
Implement a function that counts non-overlapping occurrences of a substring in a given string.
Sort characters in string
Write a function that sorts the characters in a string and returns the sorted string.
Most Common Character
Return the character that appears most frequently in a string, breaking ties by earliest occurrence.
Roman to Integer
Convert a valid Roman numeral string to an integer using standard rules.
Isomorphic Strings Check
Given two strings, check if they are isomorphic by verifying a one-to-one character mapping.
Index of First Occurrence
Implement a function that finds the starting index of a substring within a string, returning -1 when absent.
Safe Command Executor
Implement emulate_run that simulates running a command list and returns output and exit code.
Error message formatter
Write a function that constructs a formatted error message from a code, an optional context, and a fallback message.
Stack Trace Sanitizer
Implement a function that rewrites traceback file paths to basenames only.
Extract Hashtags
Extract unique hashtags from a given text string in the order they appear.
Extract mentions
Extract unique @mentions from a string, respecting email-like patterns and punctuation.
Validate time format
Check whether a given string is a valid 24-hour time in HH:MM format.
Parse Log Line
Write a function that parses a log line and returns a dictionary with timestamp, level, and message.
Replace multiple spaces
Implement a function that replaces every sequence of spaces with a single space.
Remove HTML tags
Remove all HTML tags from a string to extract clean text.
Extract Quoted Strings
Write a function that extracts the text inside every double-quoted substring from a given string.
Split on camelCase
Given a camelCase string, split it into words at uppercase letters and return them as lowercase words.
Extract domain from URL
Extract the domain (hostname without port or www) from a given URL string.
Normalize Whitespace
Write a function that normalizes any whitespace in a string to single spaces and trims the ends.
Strip Leading Zeros
Write a function that strips leading zeros from a string representing a non-negative integer.
Parse key=value pairs
Implement a parser that converts a space-separated 'key=value' string into a Python dictionary, supporting quoted values.
Find all numbers in text
Write a function that extracts all standalone integers from a text string using regular expressions.
Extract file extensions
Implement a function that extracts the extension from a filename according to standard rules.
Validate username format
Implement a function that validates a username according to length, allowed characters, and no consecutive underscores.
Replace template variables
Implement a function that replaces {{variable}} placeholders in a string using a dictionary, leaving unknown placeholders intact.
Hamming Distance
Implement a function that computes the Hamming distance between two strings of equal length.
Showing 72 challenges · easy · Strings & Text
Strings & Text — Python coding challenges
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