Support printf-style formatting? (hashtag1151)

[vikramsubramanian]

I'm looking into migrating an existing project from Python's built-in logging facilities to loguru. The code base uses printf-style formatting quite extensively, e.g.

logger.info("Loading project %s", project.name)

Unfortunately loguru doesn't seem to be plug&play in this situation, unless I'm missing something. Is there a way to have loguru support percent-style formatting? )

[mayil-ai[bot]]

Some past issues to consider:

• How to log message with args like logger.warning('hello %s', 'world') (hashtag661) | Discusses Loguru's lack of support for % formatting, similar to current issue

Here are some code snippets that may help you get started:

• loguru/_logger.py:2004-2055 | This snippet shows how loguru uses modern string formatting with curly braces {} in its logging methods. It is crucial to understand this to adapt existing printf-style logging to loguru.

Loguru does not natively support printf-style (%s) formatting. Instead, it uses {} style formatting. Here are the steps to adapt your existing code:

1. Using str.format() Method: Convert the printf-style formatting to the str.format() method.

   from loguru import logger
   
   project_name = "example_project"
   logger.info("Loading project {}".format(project_name))

2. Using f-strings (Python 3.6+): If you are using Python 3.6 or later, you can use f-strings for a more concise approach.

   from loguru import logger
   
   project_name = "example_project"
   logger.info(f"Loading project {project_name}")

3. Custom Wrapper Function: Create a wrapper function to handle the conversion from printf-style to Loguru's style.

   from loguru import logger
   
   def log_info(message, *args):
      formatted_message = message % args
      logger.info(formatted_message)
   
   project_name = "example_project"
   log_info("Loading project %s", project_name)

By following these steps, you can smoothly transition your logging from the built-in logging module to Loguru while maintaining the readability and functionality of your log messages.

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