Python logging module: Solve your toughest knowledge points

#python's logging module is a powerful tool that helps you log events and messages in your application. It provides a unified interface to configure and manage log records, allowing you to easily handle logging tasks. This article will take an in-depth look at the logging module, address common knowledge points, and provide practical examples.

Configuring logging

In order to enable logging, you must first configure a logger. This can be done via the logging.basicConfig() function. Here's how to configure a basic logger:

import logging

# 配置日志记录
logging.basicConfig(
level=logging.INFO,
fORMat="%(asctime)s - %(levelname)s - %(message)s",
filename="my_log.log",
)

In this example, we set the logging level to INFO, and specified the format of the log message and the file name of the log file.

Logging level

The logging module defines five logging levels:

• DEBUG
• INFO
• WARNING
• ERROR
• CRITICAL

The logging level determines which types of messages are logged. For example, if you set the level to INFO, only INFO level messages and higher level messages (such as WARNING and ERROR) are logged.

Log message

Use logging.info(), logging.warning() and other functions to log messages. The message can contain any string or object, for example:

logging.info("这是信息消息.")
logging.warning("这是警告消息.")

filter

Filters allow you to control which messages are logged. You can create a custom filter class or use a built-in filter such as logging.Filter. The following example uses logging.Filter to filter out messages containing a specific string:

class MyFilter(logging.Filter):
def filter(self, record):
return "my_string" not in record.msg

logging.basicConfig(
...
filters=[MyFilter()]
)

Log handler

The log handler is responsible for processing log messages. The logging module provides various built-in handlers, such as logging.StreamHandler and logging.FileHandler. Here's how to use logging.StreamHandler to output log messages to the console:

handler = logging.StreamHandler()
handler.setLevel(logging.INFO)
logging.getLogger().addHandler(handler)

Customized logging

The logging module allows you to create custom logging configurations and handlers. You can customize logging formats, create custom logging levels, and use custom filtering and processing logic.

troubleshooting

Logging is critical for troubleshooting and debugging applications. By viewing the log files, you can understand the behavior of the application and identify the source of the problem. Here are some common troubleshooting tips:

• Check the log file for error messages.
• Use logging.getLogger().getEffectiveLevel() to check the logging level.
• Verify that the logging handler is configured correctly.
• Use filters to narrow the scope of log messages.

in conclusion

Python’s logging module is a powerful tool that can enhance your application’s logging and debugging capabilities. With the knowledge provided in this guide, you will be able to effectively configure and use the logging module to solve the toughest programming challenges.

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