Python Code
Samples
Easy snippets you can copy, study, and run in the browser editor.
Export List of Dicts to CSV in Python
Write a list of dictionaries (dataframe-like) to a CSV file with headers using the standard library csv module and verify by reading it back.
import csv
def export_to_csv(data, filename):
"""Export a list of dicts to a CSV file."""
if not data:
print("No data to export")
return
# Get column names from the keys of the first dict
fieldnames = list(data[0].keys())
with open(filename, 'w', newline='', encoding='utf…Export SQLite Query Results to CSV in Python
Connects to a SQLite database, runs a query, and writes the result rows and column headers to a CSV file using the standard library.
import sqlite3
import csv
def export_query_to_csv(db_path, query, csv_path):
conn = sqlite3.connect(db_path)
cursor = conn.cursor()
cursor.execute(query)
rows = cursor.fetchall()
column_names = [description[0] for description in cursor.description]
with open(csv_path, 'w', newline='', encodi…How to Read Binary File Bytes and Inspect the Header in Python
Read the first bytes of a binary file with pathlib and display them as a hex dump plus an ASCII view to inspect file headers.
import pathlib
def inspect_binary_header(filepath: str, num_bytes: int = 16) -> None:
"""Read the first bytes of a binary file and display them as hex and ASCII."""
path = pathlib.Path(filepath)
data = path.read_bytes()[:num_bytes]
hex_str = ' '.join(f"{byte:02x}" for byte in data)
ascii_str …How to Mock Content-Disposition and Extract Filename in Python
Parse and mock Content-Disposition headers in Python to extract filenames, handling both plain and RFC 5987 encoded values.
import os
from pathlib import Path
import re
from unittest.mock import patch
def get_filename_from_content_disposition(header_value):
"""
Extract filename from a Content-Disposition header value.
Supports both filename and filename* parameters (RFC 5987).
"""
if not header_value:
return No…How to handle CORS preflight OPTIONS requests in Python
Create a mock HTTP server with a CORS preflight OPTIONS handler that returns the correct headers for browser-based API requests.
from http.server import BaseHTTPRequestHandler, HTTPServer
class CORSRequestHandler(BaseHTTPRequestHandler):
def _send_cors_headers(self):
self.send_header("Access-Control-Allow-Origin", "*")
self.send_header("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS")
self.send_head…How to Generate and Propagate W3C Trace Context Headers in Python
Generate and propagate W3C traceparent and tracestate headers for distributed tracing in Python, with mock service headers.
import uuid
def generate_w3c_traceparent(trace_id=None, parent_id=None, flags="01"):
if trace_id is None:
trace_id = uuid.uuid4().hex[:32]
if parent_id is None:
parent_id = uuid.uuid4().hex[:16]
return f"00-{trace_id}-{parent_id}-{flags}"
def create_mock_headers(service_name, trace_id=N…How to Load CSV Training Data in Python Without Pandas
Load CSV training data using Python's standard library and mock it with io.StringIO for testing, returning headers and rows as dictionaries.
import csv
from pathlib import Path
def load_csv_training_data(file_path: str | Path) -> tuple[list[str], list[dict[str, str]]]:
"""Load CSV training data and return headers plus rows as dictionaries."""
with open(file_path, mode="r", newline="", encoding="utf-8") as csv_file:
reader = csv.DictReader…How to Enforce a Strict Referrer Policy in Python
Validate HTTP headers to enforce a strict same-origin Referrer policy, accepting only origin-only URLs or absent Referer values.
import re
from unittest.mock import patch
def strict_referrer_policy(headers):
"""Return True if Referer header is absent or strictly same-origin."""
referer = headers.get("Referer")
if referer is None:
return True
# Strict-Origin-When-Cross-Origin allows same-origin full URL
# but here we…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 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…Browse by section
Each section groups closely related Python snippets.
Guide: free Python code samples library
Copy-ready Python snippets for learners and developers
PythonSkillset code samples are short, focused examples organised by topic and difficulty. Every snippet is server-rendered HTML — readable by search engines and easy to copy. Open any sample, read the notes, copy the code, then press Try in editor to run it in the browser with Pyodide.
How to use this library
- Pick a topic section — strings, lists, files, functions, and more
- Open a sample, read How it works, and copy the code block
- Run it in the IDE, tweak values, then take a related quiz or tutorial lesson
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.