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Copy-ready Python snippets by topic and difficulty — short, focused, and runnable in the browser editor.
How to Mock Environment Variables in Python
A context manager that injects and restores environment variables for isolated testing of config-dependent code.
import os
class EnvInjector:
def __init__(self, mock_vars=None):
self.mock_vars = mock_vars or {}
self.original = {}
def __enter__(self):
for key, value in self.mock_vars.items():
if key in os.environ:
self.original[key] = os.environ[key]
os.env…How to Mock Environment Variables in Python for 12-Factor Config
Read 12-factor config from env vars and test/mock them with unittest.mock.patch.dict without touching the real environment.
import os
import json
from unittest.mock import patch
def load_config(env_prefix="APP"):
"""Read 12-factor style config from env vars"""
required = ["DATABASE_URL", "API_KEY"]
optional = {"PORT": "8080", "DEBUG": "false"}
config = {}
for key in required:
full_key = f"{env_prefix}_{key…How to Mock HTTP Responses to Verify HSTS Headers in Python
This code demonstrates how to use unittest.mock to intercept and capture HTTP response headers, specifically the Strict-Transport-Security header, from a mocked HTTPServer handler for security validation.
from http.server import BaseHTTPRequestHandler, HTTPServer
from unittest.mock import patch
class StrictTransportMock(BaseHTTPRequestHandler):
def do_GET(self):
self.send_response(200)
self.send_header("Strict-Transport-Security", "max-age=31536000; includeSubDomains")
self.end_headers()
…How to Mock KMS Envelope Encryption in Python
Demonstrates a minimal mock of AWS KMS envelope encryption flow with AES-GCM data key wrapping and unwrapping.
import base64
import json
import os
import hashlib
class MockKMS:
"""Minimal mock of AWS KMS envelope encryption flow."""
def generate_data_key(self):
# Simulate KMS returning a plaintext and encrypted data key
plaintext_key = os.urandom(32)
encrypted_key = hashlib.sha256(plaintext_k…How to Mock OAuth 2.0 Device Code Flow in Python
A mock implementation of the OAuth 2.0 device authorization grant for testing authentication flows without a real provider.
import hashlib
import time
import uuid
class DeviceCodeFlowMock:
def __init__(self):
self.device_codes = {}
def request_device_code(self, client_id, scope="read write"):
device_code = uuid.uuid4().hex
user_code = str(uuid.uuid4().int)[:8].upper()
expires_in = 300
inte…How to Mock a CORS Allow Origin Whitelist in Python
A decorator-based mock of a CORS middleware that whitelists allowed origins and injects proper Access-Control-Allow-Origin headers while rejecting others.
from functools import wraps
class MockCORSConfig:
def __init__(self, allowed_origins):
self.allowed_origins = allowed_origins
def is_origin_allowed(self, origin):
return origin in self.allowed_origins
def cors_middleware(config):
def decorator(handler):
@wraps(handler)
…How to Mock a Content Security Policy Header in Python
Mock a Content-Security-Policy header locally and verify it's served correctly using Python's built-in HTTP server.
import json
from http.server import BaseHTTPRequestHandler, HTTPServer
CSP_HEADER = "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'"
class MockServer(BaseHTTPRequestHandler):
def do_GET(self):
if self.path == "/":
self.send_response(200)
self.send_header("…How to Mock a Permissions Policy in Python
A lightweight Python class that simulates a browser Permissions-Policy header by tracking allowed/ denied feature permissions with get, set, reset, and bulk operations.
class PermissionsPolicy:
def __init__(self):
self._features = {
"geolocation": "self",
"camera": "self",
"microphone": "self",
"payment": "self",
"usb": "self",
}
def get_feature_policy(self, feature):
return self._features.ge…How to Mock a Redis Session Store in Python
An in-memory RedisSessionStore class with TTL-based expiry, get/set/delete/exists methods, and JSON field support—perfect for testing and prototyping without a live Redis.
import time
import json
from collections import defaultdict
class RedisSessionStore:
"""In-memory mock of a Redis-backed session store."""
def __init__(self, ttl=3600):
self._data = defaultdict(dict)
self._expires = {}
self._ttl = ttl
def set(self, session_id, field, value):
…How to Mock a TLS Certificate Rotation Schedule in Python
Simulate a TLS certificate rotation schedule with a Python class that tracks last and next rotation dates and decides when to rotate.
import datetime
import random
import time
class CertRotator:
def __init__(self, cert_name, rotation_days=30):
self.cert_name = cert_name
self.rotation_days = rotation_days
self.last_rotated = datetime.date.today() - datetime.timedelta(days=random.randint(10, 25))
self.next_rotatio…How to Mock an mTLS Client Certificate in Python
Create a self-signed client certificate and key with OpenSSL, load them into an SSL context, and simulate an mTLS handshake in Python for testing.
import ssl
import socket
import subprocess
import tempfile
from pathlib import Path
def create_mock_certificates():
"""Generate self-signed client certificate and key for mTLS testing."""
with tempfile.TemporaryDirectory() as tmpdir:
cert_path = Path(tmpdir) / "client.crt"
key_path = Path(tmpd…How to Set X-Frame-Options DENY in Flask with a Mock Response
Set the X-Frame-Options header to DENY in a Flask response to prevent clickjacking, and verify it with Flask's test client.
from flask import Flask, Response
app = Flask(__name__)
@app.route("/")
def index():
response = Response("Hello, World!")
response.headers["X-Frame-Options"] = "DENY"
return response
if __name__ == "__main__":
with app.test_client() as client:
resp = client.get("/")
print(resp.get_da…How to Test X-Content-Type-Options nosniff in Python with Mocks
Mock httpx responses and verify that a server's X-Content-Type-Options header includes nosniff to prevent MIME sniffing.
import httpx
from unittest.mock import Mock, patch
def fetch_headers(url: str) -> dict:
response = httpx.get(url)
return dict(response.headers)
def mock_nosniff_check(response) -> bool:
content_type = response.headers.get("content-type", "")
x_content_type_options = response.headers.get("x-content-ty…How to Tune scrypt Parameters in Python
Adjust scrypt work factor (N) to hit a target hashing time with a mock benchmark loop, then return tunable parameters and a derived key.
import hashlib
def tune_scrypt_params(target_time=0.1, base_n=2**14, base_r=8, base_p=1):
"""Mock tuning of scrypt params based on target time."""
n, r, p = base_n, base_r, base_p
iterations = 0
for _ in range(5): # simple mock adjustment loop
iterations += 1
mock_time = 0.05 + (…How to implement OCSP stapling mock in Python
Simulate OCSP stapling with a caching mechanism that mocks certificate status lookups for TLS handshake validation.
import hashlib
import time
class OCSPStapler:
def __init__(self, cert_serial: str, issuer_hash: str):
self.cert_serial = cert_serial
self.issuer_hash = issuer_hash
self.cache = {}
def _mock_query_ocsp(self, serial: str) -> dict:
"""Simulate OCSP responder lookup."""
di…How to mock Argon2 password hashing in Python
This code demonstrates a mock Argon2 password hasher using HMAC-SHA256 iterations, providing hash and verify methods that mimic Argon2's salted, iterated derivation.
import hashlib
import hmac
import os
class Argon2Mock:
def __init__(self, salt_size=16, hash_len=32):
self.salt_size = salt_size
self.hash_len = hash_len
def hash(self, password: str, salt: bytes = None) -> str:
if salt is None:
salt = os.urandom(self.salt_size)
…How to mock DNS CAA record lookups in Python
Parse and filter DNS CAA records with a mock lookup function, demonstrating how certificate authorities validate domain authorization.
import dnslib
def parse_caa_record(record_string):
"""Parse a DNS CAA record string into its components."""
parts = record_string.split()
flags = int(parts[0])
tag = parts[1]
value = parts[2]
return flags, tag, value
def mock_caa_lookup(domain, caa_records):
"""Mock DNS CAA lookup that re…How to mock short TTL access tokens in Python
Simulate short-lived access tokens with a TTL, issue and validate them, and watch expiry behavior.
import time
import uuid
from datetime import datetime, timedelta
class AccessTokenManager:
def __init__(self, ttl_seconds=30):
self.ttl_seconds = ttl_seconds
self.tokens = {}
def issue_token(self):
token_id = uuid.uuid4().hex
expiry = datetime.now() + timedelta(seconds=self.t…Mock client credentials machine auth in Python
This code simulates the OAuth2 client-credentials flow for service-to-service calls, generating a mock bearer token with expiry and caching, plus a revoke method, using only the standard library.
import time
import hashlib
import secrets
class MachineAuth:
"""Mock client-credentials machine auth for service-to-service calls."""
def __init__(self, client_id, client_secret):
self.client_id = client_id
self.client_secret = client_secret
self._token = None
self._expire…OAuth2 authorization code flow mock in Python
A minimal HTTP server that mocks the OAuth2 authorization code flow, issuing codes via /authorize and exchanging them for tokens at /token.
import json
from http.server import BaseHTTPRequestHandler, HTTPServer
from urllib.parse import urlparse, parse_qs
AUTH_CODE_STORE = {}
CLIENT_ID = "demo-client"
REDIRECT_URI = "http://localhost:8000/callback"
class OAuthHandler(BaseHTTPRequestHandler):
def do_GET(self):
parsed = urlparse(self.path)
…Docker healthcheck CMD mock in Python
Runs a subprocess to curl a health endpoint and returns exit code 0 when healthy, 1 when unhealthy, mimicking a Docker HEALTHCHECK command.
import subprocess
import sys
def run_healthcheck() -> int:
result = subprocess.run(["curl", "-fsS", "http://localhost:8080/health"], capture_output=True, text=True)
if result.returncode == 0:
print("healthy")
return 0
print("unhealthy", file=sys.stderr)
return 1
if __name__ == "__ma…Generate a Mock Artifact Version Tag in Python
Creates a mock build artifact version tag from a branch name and build number, with a date stamp.
import re
from datetime import datetime
def mock_version_tag(branch_name: str, build_number: int) -> str:
"""Generate a mock build artifact version tag from branch and build number."""
branch_slug = re.sub(r'[^a-zA-Z0-9]+', '-', branch_name).strip('-').lower()
date_part = datetime.utcnow().strftime('%Y%m%…Generate a docker-compose.yml with mock services in Python
Build a docker-compose.yml string from a Python dict of service names and images, then write it to a file.
import yaml
from pathlib import Path
def generate_mock_compose(services: dict) -> str:
compose = {
"version": "3.9",
"services": {}
}
for name, image in services.items():
compose["services"][name] = {
"image": image,
"container_name": f"mock-{name}",
…How to Attach an SBOM to a Release in Python (Mock)
A mock function that attaches a Software Bill of Materials (SBOM) to a GitHub-style release by counting its components and marking the upload as attached.
import json
from pathlib import Path
def attach_sbom_mock(sbom_path: Path, release_tag: str, artifact_name: str) -> dict:
"""Mock attaching an SBOM to a release, returning the simulated upload result."""
sbom = json.loads(sbom_path.read_text())
return {
"release_tag": release_tag,
"artifa…Browse by section
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