How to Create a Log Message

In your Python code, use:

import logging

# in this case we use module name as logger name.
# You can use whatever makes sense.
logger = logging.getLogger(__name__)
logger.critical("A critical problem, such as database error.")
logger.error("A non-fatal error, such as exception raised")
logger.warning("a warning about something unusual")
logger.info("Information about some interesting event, e.g. user login")
logger.debug("messages only a developer would want to see")

For logging exceptions with a stack trace, Logger also has:

logger.exception(e)

which emits an ERROR level log message.

An example from the polls tutorial application.

def vote(request, question_id):
    """Vote for one of the polls identified by question_id."""
    ### informational (a usual event)
    logger.info(f"Vote submitted for poll #{questin_id}")
    try:
        q = Question.objects.get(id=question_id)
        choice_id = request.POST['choice_id']
        logger.info(f"Vote for choice {choice_id} on question {q}")
        choice = q.choice_set.get(pk=choice_id)
    except:
        logger.warning(
                 f"Invalid question id {question_id} or choice id {choice_id}")
        context = {'question':q, 'error_message':"Missing or invalid answer choice"}
        return render(request, 'polls/detail.html', context)

Django Standard Logging Names

Django uses some predefined loggers. You can configure loggers for these names to control how much logging is done and where the log messages go.

Logger	Description
django	Catch-all logger for django log messages.
django.request	Log HTTP requests. HTTP 4xx responses create warning log message, 5xx responses create error log messages.
django.server	When using “runserver” will log all requests with info log messages
django.template	Log errors in templates. Missing context variables logged at debug level.
django.db.backends	Log interactions with database. All SQL statements are logged at the debug level, which can be quite verbose.
django.security.xxx	Log security-related problems, including messages from a SuspiciousOperation error. These messages are not sent to the django.request logger.
django.security.csrf	Log cross-site request forgery attacks.

How to Configure Logging

Configure logging in your project’s settings.py. You can specify:

• define one or more “loggers”. For example a “console logger”, a “file logger”, or a network logger.
• which log messages (debug, info, etc.) to log to each output stream
• the format of log messages

See Django Logging Howto for details.

Example Logging Configuration

This is not guaranteed to work.

# settings.py

LOGGING = {
    'version': 1,
    'disable_existing_loggers': False,
    'formatters': {
        'details': {
            'format': '{levelname} {asctime} {module} {message}',
            'style': '{',
        },
        'simple': {
            'format': '{levelname} {message}',
            'style': '{',
        },
    },
    'handlers': {
        'file': {
            'level': 'DEBUG',
            'class': 'logging.FileHandler',
            'filename': 'polls.log',
            'formatter': 'details',
        },
        'console': {
            'level': 'INFO',
            'class': 'logging.StreamHandler',
            'formatter': 'simple',
        },
    },
    'loggers': {
        'polls': {
            'handlers': ['file', 'console'],
            'level': 'DEBUG',
            'propagate': True,
        },
    },
}

Reference

Django Logging Howto

Django Logging full documentation

Django Logging Extensions describes the various loggers that Django uses for its own messages, such as django.request and django.security.