Getting Started with the Python Logging Module: From Beginner to Expert

python The Logging module is a powerful tool for processing log messages and events. It provides rich features to help you record and monitor the behavior of your applications. This guide will take you from beginner to advanced user, introducing all aspects of the Python Logging module.

Set up logging

The first step is to set up logging. To do this, you need to import the logging module and create a Logger object. The Logger object is responsible for receiving log messages and passing them to handlers.

import logging

# 创建一个 Logger 对象
logger = logging.getLogger("my_app")

# 设置日志级别
logger.setLevel(logging.DEBUG)

Log level

The log level determines which messages are logged. The Python Logging module defines several standard levels:

• DEBUG: Detailed debugging information
• INFO: General information message
• WARNING: Potential error or problem
• ERROR: Error or exception
• CRITICAL: Critical error or application crash

Handler

Handlers are responsible for sending log messages to different destinations, such as files, consoles, or remote servers . You can use the following handlers:

# 将日志消息发送到控制台
console_handler = logging.StreamHandler()

# 将日志消息发送到文件
file_handler = logging.FileHandler("my_app.log")

Formatter

Formatters are used to customize the appearance of log messages. It allows you to specify the format of the log message, including timestamp, log level, message text, etc.

# 创建一个简单的格式化程序
fORMatter = logging.Formatter("%(asctime)s - %(levelname)s - %(message)s")

# 将格式化程序附加到处理程序
console_handler.setFormatter(formatter)

Use Logger

After setting up logging, you can use the Logger object to log messages:

logger.debug("This is a debug message.")
logger.info("This is an info message.")
logger.warning("This is a warning message.")

Advanced usage

In addition to basic functions, the Python Logging module also provides many advanced functions, such as:

• Parent/Child Logger: Create a hierarchical Logger where the child Logger can inherit the level and handler of the parent Logger.
• Filtering: Use filters to control which log messages are logged.
• Custom levels: Create your own log levels to meet specific application needs.
• Multiprocessing: Use logging in multi-process or multi-threaded applications.

Example

The following example shows how to use the Python Logging module to record application logs:

import logging

# 设置日志记录
logging.basicConfig(level=logging.INFO,
format="%(asctime)s - %(levelname)s - %(message)s",
handlers=[logging.StreamHandler()])

# 创建一个 Logger 对象
logger = logging.getLogger("my_app")

# 记录日志消息
logger.info("Application started")
logger.warning("An error occurred")

By following this guide, you can master the Python Logging module and create an effective and scalable logging system for your applications.

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