Envlog

Rust RUST_LOG-style environment variable configuration for Python's standard library logging.

Features

• Simple: One environment variable configures all loggers
• Familiar: Uses Rust's RUST_LOG syntax
• Standard: Builds on Python's logging.config.dictConfig
• Zero dependencies: Only uses Python standard library
• Flexible: Works with loggers created anywhere in your codebase

Requirements

• Python 3.8 or higher

Installation

pip install envlog

Quick Start

import logging
import envlog

# Initialize from PTHN_LOG environment variable
envlog.init()

# Now use logging normally
logger = logging.getLogger('myapp')
logger.info('Hello, world!')

# Set log level via environment
export PTHN_LOG=info
python myapp.py

Syntax

The log specification syntax follows Rust's RUST_LOG conventions:

# Set default level
PTHN_LOG=info

# Set module-specific levels
PTHN_LOG=myapp=debug

# Set default + module overrides
PTHN_LOG=warn,myapp=debug,otherlib=error

# Hierarchical modules (use . or :: separator)
PTHN_LOG=myapp.core=debug
PTHN_LOG=myapp::db=trace

# Complex example
PTHN_LOG=warn,myapp=info,myapp.db=debug,requests=error

Log Levels

Supports all standard levels (case-insensitive):

• trace → Python's DEBUG (Rust's trace is more verbose, maps to Python's lowest)
• debug → DEBUG
• info → INFO
• warn / warning → WARNING
• error → ERROR
• critical → CRITICAL

Usage Examples

Basic Usage

import envlog

# Read from PTHN_LOG environment variable
envlog.init()

# Or specify configuration directly
envlog.init(log_spec='warn,myapp=debug')

# Or use custom environment variable name
envlog.init(env_var='MY_LOG')

Module-Specific Configuration

import logging
import envlog

envlog.init(log_spec='warn,myapp.core=debug,myapp.db=trace')

# Different modules get different log levels
core_logger = logging.getLogger('myapp.core')
core_logger.debug('Detailed debugging')  # Shows (DEBUG level)

db_logger = logging.getLogger('myapp.db')
db_logger.debug('Database query')  # Shows (TRACE->DEBUG level)

other_logger = logging.getLogger('requests')
other_logger.info('HTTP request')  # Hidden (WARN level)

Custom Formatting

envlog.init(
    log_spec='debug',
    log_format='%(levelname)s %(name)s: %(message)s',
    date_format='%H:%M:%S'
)

Force Reconfiguration

# First configuration
envlog.init(log_spec='info')

# Later, reconfigure (requires force=True)
envlog.init(log_spec='debug', force=True)

# Or use reset() then init()
envlog.reset()
envlog.init(log_spec='debug')

API Reference

envlog.init()

def init(
    log_spec: Optional[str] = None,
    env_var: str = 'PTHN_LOG',
    log_format: Optional[str] = None,
    date_format: Optional[str] = None,
    force: bool = False
) -> None

Initialize logging from a RUST_LOG-style specification.

Parameters:

• log_spec: Explicit log specification (overrides env_var if provided)
• env_var: Environment variable name to read (default: 'PTHN_LOG')
• log_format: Custom log message format
• date_format: Custom date format
• force: Force reconfiguration even if already configured

envlog.reset()

def reset() -> None

Reset the configuration state, allowing init() to be called again without force=True.

envlog.parse_log_spec()

def parse_log_spec(spec: str) -> LogSpec

Parse a RUST_LOG-style specification into a LogSpec object. Useful for testing or advanced usage.

Comparison with RUST_LOG

How It Works

1. Parses RUST_LOG-style specification
2. Converts to Python logging level names
3. Generates a logging.config.dictConfig configuration
4. Applies configuration to Python's standard library logging

The logging configuration uses:

• Console handler writing to stderr
• Standard formatter with timestamp, level, logger name, and message
• Non-destructive configuration (doesn't disable existing loggers)

Development

# Clone repository
git clone https://github.com/bassmanitram/python-envlog.git
cd envlog

# Install in development mode
pip install -e ".[dev,test]"

# Run tests
pytest

# Run tests with coverage
pytest --cov=envlog --cov-report=html

License

MIT License - see LICENSE file for details

Contributing

Contributions welcome! Please open an issue or pull request.

For Developers and AI Agents

See AGENT_BOOTSTRAP.md for comprehensive project documentation including:

• Complete architecture overview
• Module-by-module code walkthrough
• Testing strategies and guidelines
• CI/CD pipeline details
• Development workflow and conventions
• Design decisions and rationale

This document provides the technical context needed to understand and contribute to the project effectively.

Acknowledgments

Inspired by Rust's env_logger crate and the RUST_LOG convention.