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Samples
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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.
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…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.
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)
…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.
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…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.
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")
…Circuit Breaker Pattern in Python for LLM API Calls
Implements a circuit breaker class that wraps LLM client calls to fail fast when the service is degrading, then recover automatically after a timeout.
import time
class CircuitBreaker:
def __init__(self, failure_threshold=3, recovery_timeout=5):
self.failure_threshold = failure_threshold
self.recovery_timeout = recovery_timeout
self.failure_count = 0
self.state = "closed"
self.last_failure_time = None
def call(self, …How to Implement an Adaptive Rate Limiter in Python
Build an adaptive rate limiter that adjusts request intervals dynamically based on recent error rates, slowing down when failures spike.
import time
import random
class AdaptiveRateLimiter:
"""Simple adaptive rate limiter that reduces requests when error rate is high."""
def __init__(self, min_interval=0.1, max_interval=2.0, error_threshold=0.3):
self.min_interval = min_interval
self.max_interval = max_interval
sel…Implement a Circuit Breaker Pattern in Python
This code implements a simple circuit breaker that opens after a threshold of consecutive failures, causing subsequent calls to fail fast without invoking the underlying function.
class CircuitBreaker:
def __init__(self, failure_threshold=3):
self.failure_threshold = failure_threshold
self.failure_count = 0
self.open = False
def call(self, func, *args, **kwargs):
if self.open:
raise RuntimeError("Circuit is open - failing fast")
try:
…Retry with Exponential Backoff and Jitter in Python
A decorator-style retry wrapper that retries a flaky function with exponential backoff plus random jitter, then raises after the last attempt fails.
import random
import time
def retry_with_backoff(func, max_retries=3, base_delay=0.5, max_jitter=0.1):
for attempt in range(max_retries + 1):
try:
return func()
except Exception as e:
if attempt == max_retries:
raise
delay = base_delay * (2 ** at…How to implement a circuit breaker in Python
A Python CircuitBreaker class that tracks failures, opens after a threshold, and retries after a timeout.
class CircuitBreaker:
def __init__(self, failure_threshold=3, timeout=5):
self.failure_threshold = failure_threshold
self.timeout = timeout
self.failure_count = 0
self.last_failure_time = None
self.state = "CLOSED"
def call(self, mock_downstream):
if self.state …Browse by section
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