Reference library

Errors & debugging

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

4 matches

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…

11 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 parse a traceback to get the last frame in Python

Extracts the innermost frame's file, line, and function name from a Python traceback object.

traceback exceptions debugging

Python

import sys
import traceback


def parse_traceback_last_frame(exc_info):
    """Return the file, line, and function of the last (innermost) frame."""
    _, _, tb = exc_info
    last_tb = tb
    while last_tb.tb_next is not None:
        last_tb = last_tb.tb_next
    filename = last_tb.tb_frame.f_code.co_filename
    l…

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")
  …

12 0 Open

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