How to Build a Robust Retry Decorator with Logging in Python

Feature Requirements

Automatically retry a function when it fails, up to N times.

Customizable retry count via max_retries (default 3).

Specify which exception types to catch (e.g., Exception or more specific).

Optional retry interval ( delay in seconds).

Preserve the original function's metadata using functools.wraps.

Full Code Implementation

import time
from functools import wraps

def retry(max_retries=3, delay=1, exceptions=(Exception,)):
    """Retry decorator.
    Args:
        max_retries (int): Maximum number of retries (default 3).
        delay (int or float): Seconds to wait between retries.
        exceptions (tuple): Exception types to catch and retry (default all Exception).
    """
    def decorator(func):
        @wraps(func)
        def wrapper(*args, **kwargs):
            retries = 0
            while retries <= max_retries:
                try:
                    return func(*args, **kwargs)
                except exceptions as e:
                    retries += 1
                    if retries > max_retries:
                        print(f"[Failed] Exceeded max retries {max_retries}, no more attempts")
                        raise
                    print(f"[Attempt {retries}/{max_retries}] Exception: {e}, retrying after {delay} seconds...")
                    time.sleep(delay)
            return None  # Should never reach here
        return wrapper
    return decorator

Example Usage

@retry(max_retries=5, delay=2, exceptions=(ConnectionError,))
def fetch_data():
    print("Fetching data...")
    # Simulate occasional failure
    import random
    if random.random() < 0.7:
        raise ConnectionError("Connection failed, please retry")
    return "Data fetched successfully"

result = fetch_data()
print(result)

Sample output:

Fetching data...

[Attempt 1/5] Exception: Connection failed, please retry, retrying after 2 seconds...

Fetching data...

[Attempt 2/5] Exception: Connection failed, please retry, retrying after 2 seconds...

Fetching data...

Data fetched successfully

Enhancement: Logging on Each Retry

Record detailed logs for every retry.

Support log level control (INFO / ERROR).

Optionally write logs to console or a file.

Retry Decorator with Logging

import time
import logging
from functools import wraps

logging.basicConfig(
    level=logging.INFO,
    format='%(asctime)s [%(levelname)s] %(message)s',
    handlers=[logging.StreamHandler()]
)

def retry(max_retries=3, delay=1, exceptions=(Exception,)):
    """Retry decorator with logging.
    Args:
        max_retries (int): Maximum retry attempts.
        delay (int or float): Seconds between retries.
        exceptions (tuple): Exception types to catch.
    """
    def decorator(func):
        @wraps(func)
        def wrapper(*args, **kwargs):
            retries = 0
            while retries <= max_retries:
                try:
                    logging.info(f"[{func.__name__}] Executing...")
                    result = func(*args, **kwargs)
                    logging.info(f"[{func.__name__}] Execution succeeded")
                    return result
                except exceptions as e:
                    retries += 1
                    logging.error(f"[{func.__name__}] Retry {retries} failed: {e}")
                    if retries > max_retries:
                        logging.error(f"[{func.__name__}] Exceeded max retries {max_retries}, aborting")
                        raise
                    logging.info(f"[{func.__name__}] Waiting {delay}s before retry {retries + 1}...")
                    time.sleep(delay)
            return None
        return wrapper
    return decorator

Logging‑Enabled Example

import random
@retry(max_retries=5, delay=2, exceptions=(ConnectionError,))
def fetch_data():
    print("Attempting to fetch data...")
    if random.random() < 0.7:
        raise ConnectionError("Simulated network outage")
    return "Data fetched successfully"

result = fetch_data()
print(result)

Sample log output:

2025-06-29 10:30:45,123 [INFO] [fetch_data] Executing...
Attempting to fetch data...
2025-06-29 10:30:45,125 [ERROR] [fetch_data] Retry 1 failed: Simulated network outage
2025-06-29 10:30:45,126 [INFO] [fetch_data] Waiting 2s before retry 2...
2025-06-29 10:30:47,130 [ERROR] [fetch_data] Retry 2 failed: Simulated network outage
2025-06-29 10:30:47,131 [INFO] [fetch_data] Waiting 2s before retry 3...
2025-06-29 10:30:49,135 [INFO] [fetch_data] Execution succeeded
Data fetched successfully