Reference library

Errors & debugging

Handle failures gracefully, raise helpful errors, and debug with confidence.

6 matches

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):
        …

14 0 Open

Errors & debugging medium

How to Log Errors with Structured Fields in Python

Logs error details as structured dictionary fields using Python's logging module with extra parameters.

logging errors structured

Python

import logging
import sys

def log_structured_error(operation: str, user_id: int, status_code: int, error_msg: str):
    """Log an error with structured fields using a dictionary."""
    logger = logging.getLogger("structured_logger")
    logger.setLevel(logging.ERROR)
    
    # Create console handler if not already …

15 0 Open

Errors & debugging medium

How to Print an Exception Chain in Python for Debugging

A helper that walks an exception's __cause__ and __context__ chain, printing each level with indentation to make debugging nested errors clearer.

exception-chain debugging traceback

Python

import sys
import traceback

def pretty_exception_chain(exc):
    """Print the full exception chain with cause/context details."""
    chain = []
    current = exc
    seen = set()
    
    while current is not None and id(current) not in seen:
        seen.add(id(current))
        chain.append(current)
        curren…

12 0 Open

Errors & debugging medium

How to Re-raise Exceptions with 'raise from' in Python

Shows how to re-raise an exception with explicit context chaining using the 'raise ... from ...' syntax, so the original cause is preserved for debugging.

exceptions raise-from error-handling

Python

def divide_with_chain(a, b):
    try:
        result = a / b
        return result
    except ZeroDivisionError as original_error:
        # Re-raise with explicit chaining context
        raise ValueError("Cannot divide by zero") from original_error

def explain_chain():
    try:
        divide_with_chain(10, 0)
    …

12 0 Open

Errors & debugging medium

How to Simulate Timeout with Custom TimeoutError in Python

Run a function in a daemon thread and raise a custom TimeoutError if it exceeds a specified time limit.

timeout threading exceptions

Python

import time
from typing import Callable, TypeVar

T = TypeVar("T")


class TimeoutError(Exception):
    """Raised when an operation exceeds its time limit."""

    def __init__(self, message: str = "Operation timed out"):
        self.message = message
        super().__init__(self.message)


def run_with_timeout(func…

13 0 Open

Errors & debugging medium

Implement circuit breaker open after failures demo in Python

A minimal CircuitBreaker class that calls a function and automatically 'opens' after a set number of consecutive failures, blocking further calls with a RuntimeError.

circuit-breaker resilience error-handling

Python

import time
from datetime import datetime


class CircuitBreaker:
    def __init__(self, threshold=3):
        self.threshold = threshold
        self.failure_count = 0
        self.is_open = False

    def call(self, func, *args, **kwargs):
        if self.is_open:
            raise RuntimeError("Circuit is OPEN")
  …

13 0 Open

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