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Calculate Time Difference Across Time Zones in Python
Compute the current time difference in hours between two time zones given their UTC offsets using Python's datetime and timezone modules.
from datetime import datetime, timezone, timedelta
def time_difference(from_tz_offset, to_tz_offset):
"""
Calculate time difference in hours between two time zones given their offsets from UTC.
Offsets are in hours (e.g., -5 for EST, +5.5 for IST).
"""
tz1 = timezone(timedelta(hours=from_tz_offset…How to Create Functions with Default Parameters in Python
This code defines two Python functions using default parameters to handle missing arguments gracefully, demonstrating how to work with optional inputs and keyword arguments.
def greet(name="Guest", greeting="Hello", punctuation="!"):
"""Generate a greeting message using default parameters."""
return f"{greeting}, {name}{punctuation}"
def create_profile(username="anonymous", age=0, city="Unknown", active=True):
"""Create a user profile dictionary with default values."""
r…How to Implement Memoized Fibonacci in Python with functools.cache
Use functools.cache to memoize a recursive Fibonacci function, avoiding repeated computation and dramatically speeding up the calculation.
from functools import cache
@cache
def fibonacci(n: int) -> int:
"""Return the n-th Fibonacci number (0-indexed)."""
if n < 2:
return n
return fibonacci(n - 1) + fibonacci(n - 2)
if __name__ == "__main__":
for i in range(10):
print(f"fibonacci({i}) = {fibonacci(i)}")
print(f"Cache…How to Invalidate Cache When Arguments Change in Python
A memoization decorator that caches function results keyed by arguments, automatically invalidating when inputs change.
from functools import wraps
def memoize(func):
cache = {}
@wraps(func)
def wrapper(*args, **kwargs):
key = (args, tuple(sorted(kwargs.items())))
if key not in cache:
cache[key] = func(*args, **kwargs)
return cache[key]
return wrapper
@memoize
def expensiv…Compound interest calculator in Python
Compute future investment value with the compound interest formula and a readable year-by-year loop.
def future_value(
principal: float,
annual_rate: float,
years: int,
compounds_per_year: int = 12,
) -> float:
"""Return balance after compound interest (rounded to cents)."""
rate_per_period = annual_rate / compounds_per_year
periods = compounds_per_year * years
amount = principal * (1 …Catch ValueError and print friendly message in Python
Wrap an int() call in a try/except block and print a friendly message when ValueError is raised.
try:
number = int("not_a_number")
except ValueError:
print("That's not a valid number. Please enter digits only.")Collect Multiple Validation Errors in Python Before Raising
A chainable Validator class that accumulates all validation errors and raises them together in a single exception.
class ValidationError(Exception):
pass
class Validator:
def __init__(self):
self.errors = []
def validate_required(self, value, field_name):
if not value:
self.errors.append(f"{field_name} is required")
return self
def validate_email(self, email):
…How to Catch ValueError in Python (try except)
Handle invalid numeric input by catching ValueError in a try/except block and returning a friendly error message.
def parse_number(text):
try:
number = int(text)
return f"Parsed number: {number}"
except ValueError as error:
return f"Error: '{text}' is not a valid number ({error})"
if __name__ == "__main__":
examples = ["42", "hello", "3.14", "100"]
for item in examples:
print(pars…How to Debug Print Behind a DEBUG Environment Flag in Python
Create a debug_print function that only outputs when the DEBUG environment variable is set to a truthy value like 1, true, yes, or on.
import os
def debug_print(*args, **kwargs):
"""Print only when DEBUG environment variable is set to a truthy value."""
if os.environ.get("DEBUG", "").lower() in ("1", "true", "yes", "on"):
print(*args, **kwargs)
if __name__ == "__main__":
# Example usage: run as `DEBUG=1 python script.py` to se…How to Handle ValueError with try-except in Python
Build a beginner-friendly division calculator that catches ValueError and ZeroDivisionError with try-except blocks.
def get_number(prompt="Enter a number: "):
while True:
try:
value = float(input(prompt))
return value
except ValueError:
print("That's not a valid number. Please try again.")
def divide_numbers(a, b):
try:
result = a / b
return result
ex…How to Validate Input and Raise TypeError in Python
Define a function that checks its argument type and raises a TypeError early with a clear message when given a non-number.
def validate_number(value):
if not isinstance(value, (int, float)):
raise TypeError(f"Expected a number, got {type(value).__name__}")
return value * 2
if __name__ == "__main__":
try:
print(validate_number(5))
print(validate_number("hello"))
except TypeError as e:
print(…How to catch ValueError in Python and print a friendly message
This code defines a function that safely converts text to an integer, catches ValueError, and prints a friendly message instead of crashing.
def parse_number(text):
try:
return int(text)
except ValueError:
print("Oops! That's not a valid number.")
return None
if __name__ == "__main__":
result = parse_number("abc")
if result is None:
print("Parsing failed.")
else:
print(f"Parsed value: {result}")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…Use pprint for Nested Structure Debug Output in Python
Pretty-print nested dictionaries and lists with pprint for readable, organized debug output.
from pprint import pprint
def build_nested_structure():
"""Create a sample nested data structure for demonstration."""
return {
"project": "DataPipeline",
"config": {
"inputs": ["raw_1.json", "raw_2.json"],
"processing": {
"steps": ["clean", "transform",…Validate try except ValueError handler for beginners — errors debugging
Learn how to validate user input and handle division errors safely using try/except with ValueError and ZeroDivisionError in Python.
def divide_numbers(a, b):
"""Divide two numbers, catching division by zero and value errors."""
try:
result = a / b
except ZeroDivisionError:
print("Error: Cannot divide by zero!")
return None
except TypeError:
print("Error: Both arguments must be numbers!")
retu…Automatically Detect Corrupted Files Using SHA-256 Checksums in Python
Compute SHA-256 checksums of files and compare them to detect corruption in Python.
import hashlib
import os
def compute_sha256(filepath: str) -> str:
"""Compute SHA-256 checksum of a file."""
sha256 = hashlib.sha256()
with open(filepath, 'rb') as f:
for chunk in iter(lambda: f.read(4096), b''):
sha256.update(chunk)
return sha256.hexdigest()
def validate_file_int…Calculate Working Hours Between Two Dates in Python
Compute total business hours (Mon-Fri, 09:00-17:00) between two datetime objects, excluding weekends and non-working hours.
from datetime import datetime, timedelta
def work_hours_between(start: datetime, end: datetime) -> float:
"""Calculate total working hours between two datetimes (Mon-Fri, 09:00-17:00)."""
def is_workday(d: datetime) -> bool:
return d.weekday() < 5
total_hours = 0.0
current = start
whi…Detect Outliers in CSV Data Using Z-Score in Python
Read a CSV file and detect outliers in a numeric column by computing z-scores, flagging those exceeding a given threshold — no machine learning required.
import csv
import statistics
from math import sqrt
def detect_outliers(csv_path, column_name, threshold=2.0):
"""Detect outliers in a numeric column using z-score method."""
values = []
with open(csv_path, 'r', newline='') as f:
reader = csv.DictReader(f)
if column_name not in reader.field…Extract a Single Member from a ZIP Archive in Python
Extract one specific file from a ZIP archive to an output directory using the standard zipfile and pathlib modules.
import zipfile
from pathlib import Path
def extract_single_member(zip_path: str, member_name: str, output_dir: str = ".") -> Path:
"""Extract a single member from a zip archive to the output directory."""
with zipfile.ZipFile(zip_path, "r") as archive:
archive.extract(member_name, output_dir)
retu…Find Duplicate Web Pages by Content Similarity in Python
Compute SHA-256 hashes of file contents to detect and report duplicate HTML pages or any files in a directory.
import hashlib
import os
from collections import defaultdict
def get_file_hash(filepath):
"""Compute SHA-256 hash of file contents."""
sha256 = hashlib.sha256()
with open(filepath, 'rb') as f:
for chunk in iter(lambda: f.read(4096), b''):
sha256.update(chunk)
return sha256.hexdiges…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 Merge Sorted Chunk Files in Python
Merge multiple sorted text files into one sorted output file using a heap for efficient k-way merging.
import heapq
def merge_sorted_chunks(chunks, output_path):
"""Merge multiple sorted iterables into single sorted output file."""
with open(output_path, "w") as out_f:
# Open all chunk files
handles = [open(chunk, "r") for chunk in chunks]
try:
# Heap of (value, index) tupl…Join two CSV files on shared key column in Python
Merge rows from two CSV files by a common key column, outputting combined records to a new file.
import csv
def join_csv(file1, file2, key, output="joined.csv"):
# Read first CSV into dict keyed by the join column
with open(file1, newline="") as f1:
reader1 = csv.DictReader(f1)
data1 = {row[key]: row for row in reader1}
# Read second CSV and merge matching rows
with open(file2, n…Build adjacency dict graph from edges in Python
Convert a list of edges into an undirected adjacency dictionary, mapping each node to its neighbors, with sorted output.
def build_adjacency_dict(edges):
graph = {}
for u, v in edges:
if u not in graph:
graph[u] = []
if v not in graph:
graph[v] = []
graph[u].append(v)
graph[v].append(u)
return graph
if __name__ == "__main__":
edges = [(1, 2), (2, 3), (3, 4), (4, 1)…Browse by section
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