Logging with Loguru in Flask

__init__.py

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from config import config
from loguru import logger
import logging

db = SQLAlchemy()

# create a custom handler
class InterceptHandler(logging.Handler):
    def emit(self, record):
        logger_opt = logger.opt(depth=6, exception=record.exc_info)
        logger_opt.log(record.levelno, record.getMessage())

# application factory pattern 
def create_app(config_name):
    app = Flask(__name__)
    app.config.from_object(config[config_name])
    config[config_name].init_app(app)
    db.init_app(app)
    # logging properties are defined in config.py
    logger.start(app.config['LOGFILE'], level=app.config['LOG_LEVEL'], format="{time} {level} {message}",
                 backtrace=app.config['LOG_BACKTRACE'], rotation='25 MB')
    
    #register loguru as handler
    app.logger.addHandler(InterceptHandler())

    # register Blueprints here
    # ...

    return app

README.md

This is a simple example of how to use loguru in your flask application

Just create a new InterceptHandler and add it to your app. Different settings should be configured in your config file, so that it is easy to change settings.

Logging is then as easy as:

from loguru import logger

logger.info("I am logging from loguru!")

config.py

import os

basedir = os.path.abspath(os.path.dirname(__file__))


class Config(object):
    SECRET_KEY = os.environ.get('SECRET_KEY') or 'SUPER-SECRET'
    LOGFILE = "log.log"

class DevelopmentConfig(Config):
    DEBUG = True
    LOG_BACKTRACE = True
    LOG_LEVEL = 'DEBUG'


class ProductionConfig(Config):
    LOG_BACKTRACE = False
    LOG_LEVEL = 'INFO'


config = {
    'development': DevelopmentConfig,
    'production': ProductionConfig,
    'default': DevelopmentConfig
}

How can I make FLASK automatically log all exception? (at least unhandled exceptions?)

@martinenkoEduard This is not possible natively. You need to define a custom exception hook instead. Here is an example: https://stackoverflow.com/questions/6234405/logging-uncaught-exceptions-in-python

How can I make FLASK automatically log all exception? (at least unhandled exceptions?)

you can use @app.errorhandler(Exception) by custom exception hook