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How to Convert camelCase to snake_case in Python
Convert camelCase strings to snake_case using a simple Python function that inserts underscores before uppercase letters and lowercases everything.
def camel_to_snake(s):
result = ""
for i, char in enumerate(s):
if char.isupper() and i > 0:
result += "_"
result += char.lower()
return result
if __name__ == "__main__":
test_cases = ["camelCase", "helloWorld", "thisIsACoolExample", "already_snake", "UPPER"]
for case i…How to Convert snake_case to Title Case in Python
Convert snake_case strings to title case by splitting on underscores, capitalizing each word, and joining them with spaces.
def to_title_case(snake_str):
words = snake_str.split("_")
return " ".join(word.capitalize() for word in words)
if __name__ == "__main__":
examples = ["hello_world", "convert_snake_case", "already_title_case", "multiple__under_scores"]
for example in examples:
print(f"{example!r:35} -> {to_tit…How to Count Vowels in a String in Python
Counts uppercase and lowercase vowels in a given string using a set and a generator expression.
def count_vowels(text):
vowels = set("aeiouAEIOU")
return sum(1 for char in text if char in vowels)
if __name__ == "__main__":
sample = "Hello, World!"
result = count_vowels(sample)
print(f"Vowel count in '{sample}': {result}")How to Count Words in a String in Python
Split a paragraph on whitespace and return the number of words using Python's built-in string methods.
def count_words(paragraph: str) -> int:
words = paragraph.split()
return len(words)
if __name__ == "__main__":
paragraph = "The quick brown fox jumps over the lazy dog."
result = count_words(paragraph)
print(f"Word count: {result}")How to Detect Expired Domains Using Python
Parse a list of domain registration data and compare expiry dates to today to find expired domains.
import datetime
# List of test domains with fake registration and expiry dates
# Format: (domain, registration_date, expiry_date)
test_domains = [
('example.com', '2020-01-15', '2024-01-15'), # Expired
('google.com', '1997-09-15', '2026-09-15'), # Still active
('test-site.org', '2019-06-01', '2023-06-0…How to Detect if a String Contains Only ASCII in Python
This code defines a function that checks whether every character in a given string is an ASCII character (Unicode code point < 128) and demonstrates it with multiple test cases.
def is_ascii_only(text: str) -> bool:
"""Return True if all characters in text are ASCII, False otherwise."""
return all(ord(char) < 128 for char in text)
if __name__ == "__main__":
# Test cases
samples = [
"Hello, world!",
"Café au lait",
"日本語テキスト",
"ASCII only 123",
…How to Encode and Decode UTF-8 in Python
Convert a Python string to UTF-8 bytes with .encode() and back to text with .decode(), with a simple demo function.
def encode_decode_demo(text: str):
encoded = text.encode("utf-8")
decoded = encoded.decode("utf-8")
print(f"Original string: {text}")
print(f"Encoded bytes: {encoded}")
print(f"Decoded string: {decoded}")
print(f"Match: {text == decoded}")
if __name__ == "__main__":
encode_decode_demo("Hel…How to Escape HTML in Python
This code demonstrates how to use Python's `html.escape` function to safely encode user input for display in HTML, preventing XSS attacks.
import html
def escape_user_input(user_input: str) -> str:
"""Escape HTML-sensitive characters for safe display."""
return html.escape(user_input)
if __name__ == "__main__":
sample_user_input = '<script>alert("XSS")</script> & \'quotes\''
safe_output = escape_user_input(sample_user_input)
print("…How to Extract Digits Only from a String in Python
This code uses a regular expression to remove all non-digit characters from a mixed string, returning only the digits.
import re
def extract_digits(text):
"""Return only the digits from the given text as a string."""
return re.sub(r'\D', '', text)
if __name__ == "__main__":
mixed = "abc123def456!@#789"
result = extract_digits(mixed)
print(result)How to Filter Text to Only Letters, Numbers, and Spaces in Python
A beginner-friendly function that filters a string to keep only alphabetic characters, digits, and spaces, removing punctuation and symbols.
def filter_text(text, keep_alpha=True, keep_digits=True, keep_spaces=True):
allowed = set()
if keep_alpha:
allowed.update("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
if keep_digits:
allowed.update("0123456789")
if keep_spaces:
allowed.add(" ")
return "".join(ch f…How to Filter a List of Strings by Keyword in Python
A helper function filters a list of strings by a keyword search with optional case sensitivity.
def filter_strings(items, keyword, case_sensitive=False):
"""
Filter a list of strings by a keyword.
Args:
items: list of strings to filter
keyword: substring to search for
case_sensitive: if True, match case exactly
Returns:
list of strings containing the keyw…How to Format Strings with Named Placeholders in Python
Format a template string using named placeholders with the str.format() method and a dictionary.
def format_named(template, data):
"""Format a template string using named placeholders."""
return template.format(**data)
if __name__ == "__main__":
template = "Hello {name}, you are {age} years old and live in {city}."
data = {"name": "Alice", "age": 30, "city": "London"}
result = format_named(t…How to Format Text in Python
A beginner-friendly helper that cleans and changes the case of a string, with options for title, upper, lower, and capitalize.
def format_text(text, case="title", strip_whitespace=True, remove_extra_spaces=True):
"""
Formats a string based on common beginner needs.
Args:
text: Input string to format
case: "title", "upper", "lower", or "capitalize"
strip_whitespace: Remove leading/trailing whitespace
…How to Format Text in Python (Beginner's Guide)
This beginner-friendly Python script demonstrates text formatting basics: stripping whitespace, converting to title case, replacing substrings, splitting into words, and generating a snippet.
text = " hello world, welcome to python skillset! "
cleaned = text.strip()
title_cased = cleaned.title()
replaced = title_cased.replace("Python", "PYTHON")
words = replaced.split()
word_count = len(words)
first_three = " ".join(words[:3])
snippet = first_three + "..."
print("Original:", repr(text))
print("Stripped:"…How to Format a Float as Currency in Python
This code defines a function that converts a float to a string formatted as US currency with two decimal places and comma separators.
def format_currency(amount):
return f"${amount:,.2f}"
if __name__ == "__main__":
test_amounts = [1234.5, 0, 9999999.999, -42.867]
for amount in test_amounts:
print(f"{amount} -> {format_currency(amount)}")How to Generate Initials from a Full Name in Python
Extract and uppercase the first letter of each word in a full name to produce initials using standard string methods.
def generate_initials(full_name):
parts = full_name.strip().split()
initials = ''.join(part[0].upper() for part in parts if part)
return initials
if __name__ == "__main__":
name = "john f. kennedy"
print(generate_initials(name))How to Generate Text Helper Functions in Python
Three simple Python functions that repeat, join, and count characters in strings for beginners.
def repeat_text(text, times):
"""Repeat a string a given number of times."""
return text * times
def join_words(words, separator=" "):
"""Join a list of words into a single string."""
return separator.join(words)
def count_characters(text):
"""Count character occurrences in a string."""
ret…How to Highlight Search Terms in Python Text
Highlights all case-insensitive occurrences of a search term in a string by wrapping them in markers.
def highlight_search_term(text: str, term: str) -> str:
"""Highlight all occurrences of term in text using terminal-style markers."""
if not term:
return text
term_lower = term.lower()
result = []
i = 0
while i < len(text):
# Check if the term starts at position i (case-insens…How to Inspect String Statistics in Python
A beginner-friendly function that returns detailed statistics about a string, including length, word count, character types, and easy text transformations.
def inspect_text(text: str) -> dict:
"""Return useful stats about a string for beginners."""
words = text.split()
return {
"length": len(text),
"word_count": len(words),
"uppercase": sum(1 for ch in text if ch.isupper()),
"lowercase": sum(1 for ch in text if ch.islower()),
…How to Join List of Words into a Sentence in Python
Concatenate a list of strings into a single sentence with spaces using the Python string join() method.
words = ["Hello", "world", "this", "is", "Python"]
sentence = " ".join(words)
print(sentence)How to Join Multiline Text with a Semicolon Separator in Python
This code joins non-empty lines of multiline text into a single string separated by semicolons, stripping leading and trailing whitespace from each line.
def join_multiline_text_with_semicolon(text):
"""Join lines of multiline text with a semicolon separator."""
lines = [line.strip() for line in text.splitlines() if line.strip()]
return "; ".join(lines)
if __name__ == "__main__":
sample_text = """First line
Second line
Third line"""
result = join_…How to Mask Credit Card Middle Digits in Python
Mask the middle digits of credit card numbers in a string, keeping only the first 8 and last 4 digits, using regular expressions.
import re
def mask_credit_card(text: str) -> str:
pattern = re.compile(r'(\d{4}[-\s]?)(\d{4}[-\s]?)(\d{4}[-\s]?)(\d{4})')
return pattern.sub(lambda m: m.group(1) + m.group(2) + '****' + m.group(4), text)
if __name__ == "__main__":
sample = "Card: 1234-5678-9012-3456 and 1111 2222 3333 4444"
print(mas…How to Merge Strings in Python
Merge multiple strings or a list of text lines into one string with a custom separator
def merge_strings(*parts, separator=" "):
"""Merge multiple string parts into one string with a separator."""
return separator.join(parts)
def merge_text_lines(lines, separator="\n"):
"""Merge a list of text lines into a single string."""
return separator.join(lines)
if __name__ == "__main__":
…How to Merge Two Strings Character by Character in Python
Interleave characters from two strings, appending any surplus characters from the longer string at the end.
def merge_texts(left: str, right: str) -> str:
"""
Merges two strings by interleaving their characters:
first char from left, first from right, then second from left,
second from right, and so on. If one string is longer, the
remaining characters are appended at the end.
Example:
merge_tex…Browse by section
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- Pick a topic section — strings, lists, files, functions, and more
- Open a sample, read How it works, and copy the code block
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Samples vs tutorials and challenges
Samples are quick reference — one concept per page. For step-by-step teaching, use our Python tutorials. To test yourself, try quizzes or coding challenges. Clean up style with the Python formatter.