How to Log Exceptions with traceback.format_exc in Python

Capture and log a full traceback string when an exception occurs using Python's traceback.format_exc() and logging module.

Easy Python 3.9+ Aug 9, 2026 Errors & debugging 14 views 0 copies

traceback logging exception debugging

Python code

18 lines

Python 3.9+

import traceback
import logging

def risky_operation(value):
    return 10 / value

logging.basicConfig(level=logging.ERROR, format='%(asctime)s - %(levelname)s - %(message)s')

def main():
    try:
        result = risky_operation(0)
        print(f"Result: {result}")
    except ZeroDivisionError:
        error_msg = traceback.format_exc()
        logging.error("Exception occurred:\n%s", error_msg)

if __name__ == "__main__":
    main()

Output

stdout

2025-04-09 14:32:15,123 - ERROR - Exception occurred:
Traceback (most recent call last):
  File "example.py", line 11, in main
    result = risky_operation(0)
  File "example.py", line 5, in risky_operation
    return 10 / value
ZeroDivisionError: division by zero

How it works

The traceback.format_exc() function returns the full traceback of the currently handled exception as a string, which is perfect for logging. The logging.basicConfig sets up a handler that writes error messages to stderr with a timestamp and level name. Inside the except block, format_exc captures the exception's traceback even though the exception was already caught. The %s placeholder in the logging call ensures the multiline traceback is formatted properly and not truncated by logging's default line handling.

Common mistakes

Using `traceback.print_exc()` instead of `format_exc()` which prints to stdout directly rather than returning a string for logging
Logging the exception object with `%s` instead of `%s` with the formatted traceback, losing stack frames
Forgetting to call `format_exc()` inside the `except` block where the exception is still active
Using `logging.exception()` which adds the traceback automatically but duplicates it if you also call `format_exc`

Variations

Replace `logging.error` with `logging.exception("message")` to auto-include the current exception's traceback
Use `logger.exception` inside an except block for a more concise alternative that appends traceback details

Real-world use cases

Logging failed API calls or database operations in a web application to diagnose issues in production.
Capturing stack traces in background job workers when tasks fail, so errors can be analyzed via log aggregation tools.
Recording full tracebacks in CLI scripts for debugging user-reported errors without exposing sensitive details in terminal output.

How to Log Exceptions with traceback.format_exc in Python

Python code

Output

How it works

Common mistakes

Variations

Real-world use cases

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