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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 Remove Duplicate Adjacent Spaces in Python
This Python function collapses any sequence of two or more adjacent spaces into a single space, preserving all other characters.
def remove_duplicate_adjacent_spaces(text):
"""Replace sequences of 2+ spaces with a single space."""
result = []
prev_was_space = False
for char in text:
if char == " ":
if not prev_was_space:
result.append(char)
prev_was_space = True
else:
…How to Remove HTML Tags in Python with Regex
Strips all HTML tags from a string using a regular expression and cleans extra whitespace.
import re
def remove_html_tags(text: str) -> str:
"""Remove all HTML tags from the given text using regex."""
# Remove opening and closing tags
clean = re.sub(r'<[^>]+>', '', text)
# Remove any extra whitespace left behind
clean = re.sub(r'\s+', ' ', clean).strip()
return clean
if __name__ ==…How to Strip Whitespace in Python
This code demonstrates how to remove leading and trailing whitespace from a string using the built-in strip() method.
def strip_whitespace(text: str) -> str:
return text.strip()
if __name__ == "__main__":
sample = " Hello, world! "
result = strip_whitespace(sample)
print(f"Original: '{sample}'")
print(f"Stripped: '{result}'")How to remove punctuation from a string in Python
Remove all punctuation characters from a string using the str.translate method and string.punctuation from the standard library.
import string
def remove_punctuation(text: str) -> str:
return text.translate(str.maketrans("", "", string.punctuation))
if __name__ == "__main__":
sample = "Hello, world! It's a test... (with punctuation) - done?"
cleaned = remove_punctuation(sample)
print(f"Original: {sample}")
print(f"Cleaned:…Remove Substring Occurrences Case-Insensitively in Python
This code removes every case-insensitive occurrence of a given substring from a text string using a simple looping approach.
def remove_occurrences_ci(text: str, substring: str) -> str:
"""Remove all case-insensitive occurrences of substring from text."""
if not substring:
return text
result = []
i = 0
lower_text = text.lower()
lower_sub = substring.lower()
sub_len = len(substring)
while i <…String helpers in Python: stats, reverse, and remove vowels
Three beginner-friendly Python functions compute text statistics, reverse word order, and strip vowels from a string.
def text_stats(text: str) -> dict:
"""Return basic statistics for a given text string."""
words = text.split()
return {
"characters": len(text),
"words": len(words),
"sentences": text.count(".") + text.count("!") + text.count("?"),
"uppercase": sum(1 for c in text if c.isupp…How to Filter Empty Strings in Python
Remove empty and whitespace-only strings from a list using a list comprehension with the strip() method.
def filter_empty_strings(strings):
"""
Filter out empty strings (including whitespace-only strings)
from a list of strings.
"""
return [s for s in strings if s.strip()]
if __name__ == "__main__":
sample_list = ["hello", "", "world", " ", "python", " ", "!"]
filtered = filter_empty_strin…How to Get the Union of Two Lists Without Duplicates in Python
Merge two lists and remove duplicate values using a set, then convert back to a list.
def union_without_duplicates(list1, list2):
return list(set(list1 + list2))
if __name__ == "__main__":
list_a = [1, 2, 3, 4]
list_b = [3, 4, 5, 6]
result = union_without_duplicates(list_a, list_b)
print(f"Union of {list_a} and {list_b}: {result}")Build a Python Script That Detects and Deletes Empty Files Across Folders
A Python script that recursively finds and removes all zero-byte files across nested directories, returning a list of deleted paths.
import os
from pathlib import Path
def find_and_delete_empty_files(root_dir: str) -> list:
"""Find and delete all empty files under root_dir. Returns list of deleted paths."""
deleted = []
for file_path in Path(root_dir).rglob('*'):
if file_path.is_file() and file_path.stat().st_size == 0:
…How to Prune Empty Directories in Python with os.walk
Remove all empty subdirectories bottom-up using os.walk with topdown=False and os.rmdir, safely ignoring non-empty folders.
import os
def prune_empty_dirs(root):
"""Remove all empty subdirectories under root, bottom-up."""
for dirpath, dirnames, filenames in os.walk(root, topdown=False):
if dirpath == root:
continue
try:
os.rmdir(dirpath)
print(f"Removed: {dirpath}")
exce…How to Diff Two Dicts in Python: Added, Removed, and Changed Keys
Compare two dictionaries and report added, removed, and changed keys using Python's set operations on dict keys.
def diff_dicts(old: dict, new: dict) -> dict:
"""Compare two dicts and report added, removed, and changed keys."""
added = {k: new[k] for k in new.keys() - old.keys()}
removed = {k: old[k] for k in old.keys() - new.keys()}
common_keys = old.keys() & new.keys()
changed = {k: (old[k], new[k]) for k …How to Remove Banned Words from a Set in Python
Filter a vocabulary set by removing banned words using the .difference() method.
vocabulary = {"apple", "banana", "cherry", "date", "elderberry"}
banned_words = {"banana", "date", "fig"}
# Remove banned words using set difference
allowed_words = vocabulary.difference(banned_words)
print("Original vocabulary:", sorted(vocabulary))
print("Banned words:", sorted(banned_words))
print("Allowed words …Graph Class with Adjacency Dict in Python
Build an undirected graph class using a dictionary of adjacency lists with methods to add vertices, edges, remove edges, and query neighbors.
class Graph:
def __init__(self):
self.adjacency = {}
def add_vertex(self, vertex):
if vertex not in self.adjacency:
self.adjacency[vertex] = []
def add_edge(self, u, v):
self.add_vertex(u)
self.add_vertex(v)
self.adjacency[u].append(v)
self.adja…How to Count Items in a Python Class
A beginner-friendly Inventory class that stores item quantities in a dictionary and provides add, remove, count, and summary methods.
class Inventory:
def __init__(self):
self.items = {}
def add(self, item, quantity=1):
self.items[item] = self.items.get(item, 0) + quantity
def remove(self, item, quantity=1):
if item not in self.items:
raise ValueError(f"{item} not in inventory")
self.items[it…How to Remove Banned Values from a List in Python
Filters a list by removing elements present in a banned set, preserving the original order.
def remove_banned(values, banned):
banned_set = set(banned)
return [item for item in values if item not in banned_set]
if __name__ == "__main__":
values = [1, 2, 3, 4, 5, 2, 6, 3, 7]
banned = [2, 3]
result = remove_banned(values, banned)
print(result)How to Remove Duplicates in Python Preserving Order
Removes duplicate items from a list while keeping the first occurrence order intact using a set for fast membership checks.
def remove_duplicates_preserving_order(items):
seen = set()
result = []
for item in items:
if item not in seen:
seen.add(item)
result.append(item)
return result
if __name__ == "__main__":
sample = [3, 1, 2, 1, 3, 4, 2, 5]
unique_items = remove_duplicates_preserv…Remove item at index without pop in Python
Remove an item at a given index from a list without using pop by slicing the list around the index.
def remove_at_index(lst, index):
"""Remove item at index and return the new list."""
if index < 0 or index >= len(lst):
raise IndexError("Index out of range")
return lst[:index] + lst[index + 1:]
if __name__ == "__main__":
items = [10, 20, 30, 40, 50]
result = remove_at_index(items, 2)
…How to Strip EXIF Metadata from Images in Python
Remove EXIF metadata from image bytes using Pillow, with a mock JPEG generator for testing.
from PIL import Image
from PIL.ExifTags import TAGS
from io import BytesIO
import struct
def strip_exif(image_bytes, remove_metadata=True):
"""Remove EXIF metadata from image bytes."""
img = Image.open(BytesIO(image_bytes))
if remove_metadata:
# Clear all metadata
img.info.clear()
# Sa…How to Filter Git History to Remove Secret File Entries in Python
A pure-Python mock that filters a repository's history to drop any commit that touched a secret file, so you can plan a cleanup before rewriting Git history.
from pathlib import Path
import json
def filter_history(history, secret_path):
"""Remove entries that touch the secret file."""
return [entry for entry in history if secret_path not in entry["files"]]
if __name__ == "__main__":
repo_history = [
{"commit": "a1b2c3", "message": "Add app", "files": …How to Mock Git Clean Dry Run in Python
Simulate the output of `git clean -n` in Python to preview which untracked files would be removed without actually deleting them.
import subprocess
import sys
def mock_git_clean_dry_run(untracked_files):
"""Simulate `git clean -n` for a given list of untracked files."""
if not untracked_files:
print("No untracked files to remove.")
return
print("Would remove:")
for file in untracked_files:
print(f" {fil…How to compute diff stats (insertions, deletions) in Python
Parses a git diff text and counts the number of added and removed lines to produce insertion and deletion stats.
import re
from collections import Counter
def parse_diff(diff_text):
insertions = 0
deletions = 0
for line in diff_text.splitlines():
if line.startswith("+") and not line.startswith("+++"):
insertions += 1
elif line.startswith("-") and not line.startswith("---"):
d…How to Build a Simple Data Helper in Python for API Design
Create a beginner-friendly DataHelper class that demonstrates basic CRUD operations (add, get, list, remove) using an in-memory dictionary, ideal for learning API design concepts.
class DataHelper:
"""Simple data helper for beginners learning API design concepts."""
def __init__(self):
self._data = {}
def add_record(self, key, value):
"""Add a record to the store."""
self._data[key] = value
return f"Added: {key} -> {value}"
def get_…How to do feature selection with VarianceThreshold in Python
This code demonstrates how to use scikit-learn's VarianceThreshold to remove low-variance features from a NumPy array, keeping only those that vary enough to be useful for modeling.
import numpy as np
from sklearn.feature_selection import VarianceThreshold
def main():
# Mock dataset: 4 samples, 5 features
X = np.array([
[0.1, 0.2, 1.0, 1.0, 0.5],
[0.2, 0.2, 0.0, 1.0, 0.4],
[0.1, 0.2, 1.0, 1.0, 0.6],
[0.3, 0.2, 1.0, 0.0, 0.5]
])
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