Getting Started

Logly is a high-performance logging library for Python powered by a Rust engine built with PyO3. It provides a clean API with 10 built-in log levels, flexible sinks, file rotation, compression, and first-class framework integrations.

Installation

pip

pip install logly

uv

uv add logly

Poetry

poetry add logly

From Source

git clone https://github.com/muhammad-fiaz/logly.git
cd logly
uv sync
uv run maturin develop

System Requirements

• Python 3.10 or later
• Rust toolchain (for building from source)
• Supported platforms: Linux, macOS, Windows

Verifying Installation

import logly

print(logly.__version__)

Basic Usage

Start Logging

from logly import logger

logger.info("Application started")
logger.debug("Debug info")
logger.warning("Something looks off")
logger.error("An error occurred")
logger.success("Operation completed!")

Use Different Levels

Logly has 10 built-in levels organized by severity:

Level	Numeric	Description
TRACE	5	Finer-grained than DEBUG
DEBUG	10	Diagnostic information
INFO	20	General information
NOTICE	25	Normal but significant
SUCCESS	30	Successful operations
WARNING	40	Unexpected behavior
ERROR	50	Serious problems
FAIL	55	Operation failures
CRITICAL	60	Critical system errors
FATAL	70	Unrecoverable errors

from logly import logger

logger.trace("Trace message")
logger.debug("Debug message")
logger.info("Info message")
logger.notice("Notice message")
logger.success("Success message")
logger.warning("Warning message")
logger.error("Error message")
logger.fail("Fail message")
logger.critical("Critical message")
logger.fatal("Fatal message")

Set the Minimum Level

from logly import logger

# Only show WARNING and above
logger.add("stdout", level="WARNING")

Log to Files

Add a File Sink

from logly import logger

# Basic file logging
logger.add("app.log")

# With rotation and retention
logger.add(
    "app.log",
    level="INFO",
    rotation="daily",
    retention="30 days",
    compression="gzip",
)

logger.info("This goes to the file")

Multiple Sinks

from logly import logger

logger.add("app.log", level="DEBUG", rotation="daily")
logger.add("errors.log", level="ERROR", retention="90 days")
logger.add("stdout", level="INFO", colorize=True)

logger.info("All three sinks receive this")

Bind Context

Attach persistent metadata to a logger:

from logly import logger

user_logger = logger.bind(user_id="12345", request_id="abc-789")
user_logger.info("User logged in")
# Output includes: user_id=12345 request_id=abc-789

Catch Exceptions

Automatically log exceptions without crashing:

from logly import logger

with logger.catch():
    risky_operation()

# Or with options
with logger.catch(reraise=True):
    dangerous_call()

# Exclude specific exceptions
with logger.catch(exclude=ValueError):
    optional_operation()

Framework Integrations

FastAPI

from fastapi import FastAPI
from logly.integrations.fastapi import LoglyMiddleware

app = FastAPI()
app.add_middleware(LoglyMiddleware)

Django

# settings.py
LOGGING = {
    "handlers": {
        "logly": {
            "()": "logly.integrations.django.LoglyHandler",
            "level": "INFO",
        },
    },
    "root": {
        "handlers": ["logly"],
        "level": "INFO",
    },
}

Flask

from flask import Flask
from logly.integrations.flask import init_app

app = Flask(__name__)
init_app(app)

Async Logging

Logly handles async through queue-based workers, not asyncio. Enable with enqueue=True:

from logly import logger

logger.add("app.log", enqueue=True)

# All log calls remain synchronous
# A background worker processes the queue

Next Steps

• Sinks - Learn about all sink types
• Console & Output Control - Enable/disable console and file output
• Source Location & Timestamps - Customize file info and timestamps
• Formatting - Customize output format
• Filtering - Control which messages pass through
• Context Binding - Attach metadata to logs
• Rotation & Retention - Manage log files
• Custom Levels - Register your own log levels
• Concurrency - Thread-safe background logging
• Integrations - Connect to FastAPI, Django, Flask, and more

Troubleshooting

If you encounter issues, check the Troubleshooting Guide or FAQ.