commentlogger 0.9

Turn comments into logs

commentlogger

Convert your inline comments into log lines during development

pip install commentlogger

The Problem

My motivation is highly opinionated. If you have similar pain points, this project may be for you :)

As developers, we face a dilemma:

• During development: We want clean, readable code without log statements cluttering our logic
• In production: We need comprehensive logging to debug issues

Writing logging statements while developing can make code harder to read and understand. But we still want to trace execution flow during debugging.

commentlogger solves this by letting you write natural inline comments during development, then automatically logging them as your code executes.

Features

• 🎯 Zero code clutter - Your comments become your logs
• 🔍 Line-by-line execution tracing - See exactly what's running and when
• 🎨 Flexible logger support - Use your own logger or the default
• 📊 Log level support - Specify log levels directly in comments (DEBUG, INFO, WARNING, ERROR, CRITICAL)
• 🚫 Stopword filtering - Comments starting with certain user-specified keywords (like TODO, FIXME, NOTE, HACK, XXX, BUG) are automatically skipped and won't be logged
• 🚀 Development-focused - Designed for debugging, not production (see Performance note)
• 📝 Clean syntax - Simple decorator, nothing more
• 🔄 Production converter - Tool to convert development code to production-ready logging

Quick Start

import logging
from commentlogger import logcomments

logging.basicConfig(level=logging.INFO, format='%(message)s')
logger = logging.getLogger(__name__)

@logcomments(logger)
def foo(a, b):
    a += 1  # increment for stability
    b *= 2  # multiply for legal compliance
    
    # compute sum
    answer = a + b
    return answer

def bar(a, b):
    a += 1  # increment for stability
    b *= 2  # multiply for legal compliance
    
    # compute sum
    answer = a + b
    return answer

if __name__ == "__main__":
    print('starting')
    
    foo(2, 3)  # Comments are logged
    bar(1, 2)  # No decorator, no logging
    
    print('done')

Output:

starting
[foo:12] increment for stability
[foo:13] multiply for legal compliance
[foo:16] compute sum
done

Notice that bar() doesn't produce any log output because it's not decorated.

Usage

Basic Usage

from commentlogger import logcomments

@logcomments()  # Uses default logger
def my_function():
    # This comment will be logged
    x = 1
    return x

Custom Logger

import logging
from commentlogger import logcomments

# Create your custom logger
logger = logging.getLogger('myapp')
logger.setLevel(logging.DEBUG)

@logcomments(logger)
def my_function():
    # This uses your custom logger
    x = 1
    return x

Log Levels in Comments

You can specify log levels directly in your comments using the format # LEVEL: message:

import logging
from commentlogger import logcomments

logging.basicConfig(level=logging.DEBUG, format='%(levelname)s: %(message)s')
logger = logging.getLogger(__name__)

@logcomments(logger)
def process_transaction(amount):
    # DEBUG: Starting transaction processing
    validated = validate_amount(amount)
    
    # INFO: Transaction validated successfully
    result = apply_transaction(validated)
    
    # WARNING: High value transaction detected
    if result > 10000:
        alert_compliance()
    
    # ERROR: Transaction amount is negative
    if result < 0:
        rollback()
        
    # This is a regular info message (no level specified)
    return result

Output:

DEBUG: Starting transaction processing
INFO: Transaction validated successfully
WARNING: High value transaction detected
INFO: This is a regular info message

Stopword Filtering

You can specify stopwords to prevent certain comments from being logged:

import logging
from commentlogger import logcomments

logging.basicConfig(level=logging.INFO, format='%(message)s')
logger = logging.getLogger(__name__)

@logcomments(logger, stopwords=['TODO', 'FIXME', 'NOTE'])
def process_data(data):
    # TODO: optimize this algorithm later
    validated = validate(data)
    
    # Processing data now
    result = transform(validated)
    
    # FIXME: handle edge case for empty lists
    if result:
        return result[0]
    
    # NOTE: this is a temporary workaround
    return None

Only comments that don't start with a stopword prefix is logged. Comments starting with TODO, FIXME, or NOTE are silently skipped.

Supported log levels:
These are the default log levels in python's logging module. If you'd like additional/custom log levels, ensure you add them before you pass the logger to the logcomments decorator

• DEBUG (or D, DEB, DEBU, debu)
• INFO (or I, INF, inf)
• WARNING (or W, WARN, WA, wa)
• ERROR (or E, ERR, ER, er)
• CRITICAL (or C, CRIT, CRI, cri)

Shorthand matching:

• Comments are case-insensitive for level matching
• Prefix matches work: # warn: message → WARNING level
• If multiple levels share a prefix, the lexicographically first is used
• If no level is specified or recognized, defaults to INFO

Multiple Naming Styles

The package supports different naming conventions:

from commentlogger import logcomments
from commentlogger import logComments  # camelCase
from commentlogger import log_comments # snake_case alternative

# All three work identically
@logcomments(logger)
@logComments(logger)
@log_comments(logger)

How It Works

commentlogger uses Python's sys.settrace() mechanism to intercept line-by-line execution. When a decorated function runs:

1. The decorator extracts all comments from the function's source code
2. As each line executes, it checks if that line has a comment
3. If a comment exists, it parses the log level (if specified) and message
4. It logs the message at the appropriate level before executing the line
5. Execution continues normally

Log level parsing:

• Format: # LEVEL: message (e.g., # DEBUG: Entering function)
• If no level is specified (e.g., # message), defaults to INFO
• Supports shorthand: # W: message matches WARNING
• Case-insensitive matching

Performance Considerations

⚠️ Important: commentlogger uses sys.settrace() which has significant performance overhead (10-30x slower).

Recommended usage:

• ✅ Development and debugging
• ✅ Local testing
• ✅ Understanding complex logic flow
• ❌ Production environments
• ❌ Performance-critical code
• ❌ Automated test suites

Transition to Production

When you're ready to move to production, you have several options:

1. Remove the decorator (simplest)

Just remove @logcomments(logger) from your functions.

2. Convert to explicit logging (recommended)

Use the included inject_logging.py tool to automatically convert your commented code to production-ready logging:

python prod.py -i mycode.py -o mycode_production.py

Input code:

import logging

from commentlogger import logcomments

logger = logging.getLogger(__name__)

@logcomments(logger)
def process_data(x):
    x = validate(x)  # DEBUG: Starting data processing
    result = transform(x)  # INFO: Data validated
    
    if len(result) > 1000:  # WARNING: Large dataset detected
        optimize()
    
    return result

Output code:

import logging

logger = logging.getLogger(__name__)

def process_data(x):
    logger.debug("Starting data processing")
    x = validate(x)  # DEBUG: Starting data processing
    
    logger.info("Data validated")
    result = transform(x)  # INFO: Data validated
    
    logger.warning("Large dataset detected")
    if len(result) > 1000:  # WARNING: Large dataset detected
        optimize()
    
    return result

The tool:

• Automatically detects your logger variable name from the decorator
• Preserves log levels from comments
• Removes the @logcomments decorator
• Only processes decorated functions
• Works with any import alias (e.g., from commentlogger import logcomments as trace)

Philosophy

This tool embodies a simple idea: during development, your comments already describe what your code does. Why write them twice - once as comments and again as log statements?

commentlogger lets you:

• Write cleaner development code
• Maintain readability
• Debug with detailed execution traces
• Specify appropriate log levels inline
• Transition to production logging when ready

Requirements

• Python 3.7+
• No external dependencies (uses only standard library)

Contributing

Contributions welcome! Please feel free to submit a Pull Request.

License

MIT License - see LICENSE file for details

Author

Created with ❤️ for developers who value clean, readable code.

See Also

• Python logging documentation
• sys.settrace() documentation

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Note: Remember that commentlogger is a development tool. For production logging, use explicit logger calls or generate them programmatically from your development code using the included conversion tool.