Errors & debugging
Handle failures gracefully, raise helpful errors, and debug with confidence.
How to Configure Python Logging with File Rotation
A complete demo that sets up a logger with a rotating file handler, writes several log entries, and shows the contents of the current log file.
import logging
from logging.handlers import RotatingFileHandler
logger = logging.getLogger("rotating_logger")
logger.setLevel(logging.DEBUG)
file_handler = RotatingFileHandler(
"app.log",
maxBytes=100,
backupCount=3
)
file_handler.setFormatter(
logging.Formatter("%(asctime)s - %(levelname)s - %(messa…How to Debug Print Behind a DEBUG Environment Flag in Python
Create a debug_print function that only outputs when the DEBUG environment variable is set to a truthy value like 1, true, yes, or on.
import os
def debug_print(*args, **kwargs):
"""Print only when DEBUG environment variable is set to a truthy value."""
if os.environ.get("DEBUG", "").lower() in ("1", "true", "yes", "on"):
print(*args, **kwargs)
if __name__ == "__main__":
# Example usage: run as `DEBUG=1 python script.py` to se…Browse by section
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Errors & debugging — Python code examples
What you will find here
This page collects errors & debugging snippets — short, copy-ready Python you can paste into our free online IDE and run without installing anything. Each sample includes a plain-English explanation and the full source code.
Samples vs tutorials and challenges
Samples are quick reference — one concept per page. For step-by-step teaching, use our Python tutorials. To test yourself, try quizzes or coding challenges. Clean up style with the Python formatter.