{"id":20566,"date":"2018-05-09T09:57:08","date_gmt":"2018-05-09T13:57:08","guid":{"rendered":"https:\/\/www.bloomberg.com\/company\/stories\/guide-logging-python\/"},"modified":"2022-02-16T12:35:51","modified_gmt":"2022-02-16T17:35:51","slug":"guide-logging-python","status":"publish","type":"post","link":"https:\/\/www.bloomberg.com\/company\/stories\/guide-logging-python\/","title":{"rendered":"A guide to logging in Python"},"content":{"rendered":"
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Get a better understanding of logging in Python with this primer by Senior Software Developer Mario Corchero.<\/em><\/p>\n

This article was originally\u00a0published on Opensource.com<\/a>\u00a0<\/span>under the\u00a0<\/span>CC BY-SA 4.0<\/a>\u00a0<\/span>license.<\/em><\/p>\n\n<\/div>\n

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\"A<\/h2>\n

Image by:\u00a0Pixabay<\/a>.\u00a0CC0 1.0<\/a>.<\/h6>\n<\/div>\n<\/div>\n
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There is little worse as a developer than trying to figure out why an application is not working if you don\u2019t know what is going on inside it. Sometimes you can\u2019t even tell whether the system is working as designed at all.<\/p>\n

When applications are running in production, they become black boxes that need to be traced and monitored. One of the simplest, yet most important ways to do so is by logging. Logging allows us\u2014at the time we develop our software\u2014to instruct the program to emit information while the system is running that will be useful for us and our sysadmins.<\/p>\n

The same way we document code for future developers, we should direct new software to generate adequate logs for developers and sysadmins. Logs are a critical part of the system documentation about an application\u2019s runtime status. When instrumenting your software with logs, think of it like writing documentation for developers and sysadmins who will maintain the system in the future.<\/p>\n

Some purists argue that a disciplined developer who uses logging and testing should hardly need an interactive debugger. If we cannot reason about our application during development with verbose logging, it will be even harder to do it when our code is running in production.<\/p>\n

This article looks at Python\u2019s\u00a0logging\u00a0<\/strong>module, its design, and ways to adapt it for more complex use cases. This is not intended as documentation for developers, rather as a guide to show how the Python\u00a0logging\u00a0<\/strong>module is built and to encourage the curious to delve deeper.<\/p>\n

Why use the logging module?<\/h2>\n

A developer might argue, why aren\u2019t simple print statements sufficient? The\u00a0logging<\/b>\u00a0module offers multiple benefits, including:<\/p>\n