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Copy-ready Python snippets by topic and difficulty — short, focused, and runnable in the browser editor.
Automatically Detect Weak Passwords from Large Password Lists in Python
This Python script identifies weak passwords from a list by checking length, common patterns, sequential characters, and uniform characters, returning those that fail the security checks.
import re
COMMON_PASSWORDS_FILE = "common_passwords.txt"
def is_weak(password):
# Check length
if len(password) < 8:
return True
# Check for common patterns
if password.lower() in {"password", "123456", "qwerty", "letmein", "admin", "welcome"}:
return True
# Check for sequential c…Build a Secure Password Strength Checker in Python
A Python function that evaluates password strength based on length and character diversity, returning Weak, Moderate, or Strong.
import re
def password_strength(password: str) -> str:
score = 0
if len(password) >= 8:
score += 1
if re.search(r'[a-z]', password):
score += 1
if re.search(r'[A-Z]', password):
score += 1
if re.search(r'\d', password):
score += 1
if re.search(r'[!@#$%^&*(),.?":…How to Detect PII in Documents Using Python
Use regex patterns to automatically detect emails, phone numbers, SSNs, and credit card numbers in text documents.
import re
from typing import List, Dict
def detect_pii(text: str) -> Dict[str, List[str]]:
patterns = {
"email": r"[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}",
"phone": r"\(?\d{3}\)?[-.\s]?\d{3}[-.\s]?\d{4}",
"ssn": r"\b\d{3}-\d{2}-\d{4}\b",
"credit_card": r"\b\d{4}[- ]?\d{4}[-…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 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…Redact secrets from log message formatter in Python
Build a custom logging.Formatter that masks passwords, API keys, and credit card numbers in log output.
import re
import logging
class RedactingFormatter(logging.Formatter):
"""Formatter that masks sensitive data in log messages."""
SENSITIVE_PATTERNS = [
(re.compile(r'password[=:]\s*\S+', re.IGNORECASE), 'password=[REDACTED]'),
(re.compile(r'api[_-]?key[=:]\s*\S+', re.IGNORECASE), 'api_key…Audit File Permissions Across a Project in Python
Walks through every file and directory in a project tree and prints POSIX permissions plus owner UID.
import os
import stat
from pathlib import Path
def audit_file_permissions(project_root):
"""Walk through project_root and print path, owner, and permissions for every file."""
results = []
for root, dirs, files in os.walk(project_root):
for name in files + dirs:
full_path = os.path.joi…Build a Secure Local Password Vault with Encrypted Storage in Python
A Python class that stores and retrieves passwords in an encrypted JSON file using Fernet symmetric encryption from the cryptography library.
import json
import os
import base64
import hashlib
from cryptography.fernet import Fernet
from getpass import getpass
class PasswordVault:
def __init__(self, vault_file="vault.json", key_file="vault.key"):
self.vault_file = vault_file
self.key_file = key_file
self.key = self._load_or_creat…Encrypt and Decrypt Files Using Python
Encrypt and decrypt files using the cryptography library's Fernet symmetric encryption.
import os
from pathlib import Path
from cryptography.fernet import Fernet
def generate_key(key_file: Path) -> bytes:
key = Fernet.generate_key()
key_file.write_bytes(key)
return key
def load_key(key_file: Path) -> bytes:
return key_file.read_bytes()
def encrypt_file(input_path: Path, key: bytes, out…How to Compute File SHA256 Hash with hashlib in Python
Compute the SHA256 hash of a file by reading it in chunks with hashlib and Path.open.
import hashlib
from pathlib import Path
def sha256_file(file_path: Path) -> str:
sha256_hash = hashlib.sha256()
with file_path.open("rb") as f:
for chunk in iter(lambda: f.read(4096), b""):
sha256_hash.update(chunk)
return sha256_hash.hexdigest()
if __name__ == "__main__":
demo_fi…How to Load Pickle Files Safely in Python
This code demonstrates how to load pickle files safely in Python by using a restricted unpickler that only allows specific, trusted classes, preventing arbitrary code execution from untrusted pickles.
import pickle
# Default pickle.load is unsafe: it executes arbitrary code when unpickling.
class Unsafe:
def __reduce__(self):
return (eval, ("open('/tmp/pickle_demo.txt', 'w').write('pwned')",))
# Create a malicious payload (simulating untrusted source)
malicious_data = pickle.dumps(Unsafe())
# Safe ap…Parameterize SQL queries in Python to prevent SQL injection
Safely fetch users from a SQLite database using parameterized queries to prevent SQL injection attacks.
import sqlite3
def get_users_by_name(name):
"""Fetch users safely using parameterized query."""
conn = sqlite3.connect(':memory:')
cursor = conn.cursor()
# Create sample table and data
cursor.execute('CREATE TABLE users (id INTEGER, name TEXT)')
cursor.executemany('INSERT INTO users (name…How to Detect Hardcoded Secrets in Python Source Code
A Python utility that scans source code for common hardcoded secrets like API keys, passwords, tokens, and AWS credentials using regex patterns.
import re
def detect_secrets(text):
"""Detect potential hardcoded secrets in source code."""
patterns = {
'api_key': r'(?i)(api[_-]?key|apikey)\s*[=:]\s*["\']([^"\']+)["\']',
'password': r'(?i)(password|passwd)\s*[=:]\s*["\']([^"\']+)["\']',
'token': r'(?i)(\b(token|secret)\b)\s*[=:]\s…Demonstrate Prompt Injection Bypass in Python
Simulate why naive system prompt filters fail against prompt injection with casing and spacing variations.
# Demonstrate why system prompts can be bypassed by simulated user input
# This demo shows a naive filter being ignored via prompt injection
def process_user_message(message, system_rules):
"""Simulate an AI that follows system rules but gets tricked."""
# Claim to check system rules
for rule in system_ru…How to Detect Prompt Injection in Python
Implements a regex-based heuristic in Python to flag common prompt injection attempts before sending input to an LLM.
import re
def contains_prompt_injection(user_input: str) -> bool:
# Directives to ignore previous instructions or act as system
ignore_patterns = [
r"\bignore\s+(all\s+)?previous\s+instructions\b",
r"\bdisregard\s+(all\s+)?previous\s+instructions\b",
r"\bdon'?t\s+follow\s+(any\s+)?inst…How to Filter Blocked Words in Python
Scans input text against a moderation blocklist, returning blocked terms and their counts.
MODERATION_BLOCKLIST = {"spam", "scam", "fraud", "phishing", "malware", "abuse"}
def scan_text(text: str) -> dict:
normalized = text.lower()
words = normalized.replace(".", " ").replace(",", " ").replace("!", " ").replace("?", " ").split()
found_terms = []
for word in words:
if word in MO…Find Sensitive Information in Log Files with Python
Scan log files for emails, IP addresses, API keys, and passwords using regular expressions in Python.
import re
import os
from pathlib import Path
def find_sensitive_info(log_path):
"""Scans log files for patterns like emails, IPs, API keys, and passwords."""
patterns = {
'Email': r'[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}',
'IP Address': r'\b(?:\d{1,3}\.){3}\d{1,3}\b',
'API Key'…Generate Strong Random Passwords with Custom Rules in Python
Build a configurable password generator using Python's secrets module that lets you toggle lowercase, uppercase, digits, and punctuation.
import secrets
import string
def generate_password(length=16, use_lower=True, use_upper=True, use_digits=True, use_punct=True):
pool = ''
if use_lower:
pool += string.ascii_lowercase
if use_upper:
pool += string.ascii_uppercase
if use_digits:
pool += string.digits
if use_pu…Generate Strong SSH Keys and Save Them Securely with Python
Generate a 4096-bit RSA SSH key pair using Python's cryptography library and save both private and public keys with restricted file permissions.
import os
import stat
from pathlib import Path
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import rsa
from cryptography.hazmat.backends import default_backend
def generate_ssh_keypair(key_path: str = "id_rsa", passphrase: str = None):
"""Generate a 4096-…How to Detect Recently Installed Software in Python
Uses subprocess to call pip and parse package metadata to list recently installed Python packages.
import subprocess
import sys
from datetime import datetime, timedelta
def detect_recently_installed(days=7):
"""Detect recently installed software packages."""
recent_packages = []
cutoff_date = datetime.now() - timedelta(days=days)
try:
# For pip-installed packages (Python packages)
…How to Quarantine Suspicious Files in Python
Move files with suspicious extensions to a quarantine folder using pathlib and shutil for safe isolation.
import shutil
import os
from pathlib import Path
def quarantine_files(source_dir, quarantine_dir, suspicious_extensions):
"""
Move files with suspicious extensions to a quarantine folder.
Returns list of moved files.
"""
source_path = Path(source_dir)
quarantine_path = Path(quarantine_dir)
…How to Scan Configuration Files for Security Issues in Python
Automatically scan configuration files for common security mistakes using regex rules in Python.
import re
import os
from pathlib import Path
SECURITY_RULES = [
(r'^#\s*INSECURE_', 'Insecure comment starts with # INSECURE_'),
(r'password\s*=\s*("|\\\')?[^"\\\'"\s]+("|\\\')?$', 'Hardcoded password'),
(r'debug\s*=\s*True', 'Debug mode enabled'),
(r'[Pp]ermit[Rr]ootLogin\s+yes', 'PermitRootLogin ena…How to Scan Files Against a Malware Hash List in Python
Compare a file's SHA-256 hash against a known malware hash set and report whether it's clean or infected.
import hashlib
from pathlib import Path
# Mock file content (in real usage, read from disk)
MOCK_FILE_CONTENT = b"print('hello world')"
KNOWN_MALWARE_HASHES = {
"8d969eef6ecad3c29a3a629280e686cf0c3f5d5a86aff3ca12020c923adc6c92",
"5e884898da28047151d0e56f8dc6292773603d0d6aabbdd62a11ef721d1542d8",
}
def sha25…How to Scan Open Ports on a Host with Python
A Python function that uses socket.connect_ex to check for open TCP ports on a given host within a range and returns a list of open ports.
import socket
def scan_ports(host, start_port, end_port):
open_ports = []
for port in range(start_port, end_port + 1):
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.settimeout(0.5)
result = sock.connect_ex((host, port))
if result == 0:
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