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structlog is the production-ready logging solution for Python:

• Simple: Everything is about functions that take and return dictionaries – all hidden behind familiar APIs.
• Powerful: Functions and dictionaries aren’t just simple but also powerful. structlog leaves you in control.
• Fast: structlog is not hamstrung by designs of yore. Its flexibility comes not at the price of performance.

Thanks to its flexible design, you choose whether you want structlog to take care of the output of your log entries or whether you prefer to forward them to an existing logging system like the standard library's logging module.

The output format is just as flexible and structlog comes with support for JSON, logfmt, as well as pretty console output out-of-the-box:

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Introduction

structlog has been successfully used in production at every scale since 2013, while embracing cutting-edge technologies like asyncio, context variables, or type hints as they emerged. Its paradigms proved influential enough to help design structured logging packages across ecosystems.

Project Links

• Get Help (use the structlog tag on Stack Overflow)
• PyPI
• GitHub
• Documentation
• Changelog
• Third-party Extensions

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Release Information

Added

• Add structlog.stdlib.render_to_log_args_and_kwargs processor. Same as structlog.stdlib.render_to_log_kwargs, but also allows to pass positional arguments to logging. With it, you do not need to add structlog.stdlib.PositionalArgumentsFormatter processor to format positional arguments from structlog loggers. #668

• Native loggers now have is_enabled_for() and get_effective_level() methods that mirror the behavior of the standard library's logging.Logger.isEnabledFor() and logging.Logger.getEffectiveLevel(). #689

Changed

• structlog.typing.BindableLogger protocol now returns Self instead of BindableLogger. This adds a dependency on typing-extensions for Pythons older than 3.11. #642 #659

• structlog.dev.ConsoleRenderer will quote string value with special characters. #647

• structlog.stdlib.recreate_defaults() now also adds structlog.stdlib.PositionalArgumentsFormatter. In default native mode, this is done by the loggers at the edge.

• structlog.make_filtering_bound_logger() now also accepts a string for min_level.

Fixed

• Fix handling calls to {logger}.exception() outside of exception blocks. Depending on the structlog configuration, this either resulted in an event dict key exception: "MISSING" or lead to an error. Now, an invalid or missing exc_info will just be ignored. This means, that calling {logger}.exception() outside of an exception block is basically the same as calling {logger}.error(). #634 #680

• Instantiating structlog.dev.ConsoleRenderer does not mutate the passed styles dict anymore. #669

• The native FilteringBoundLogger.fatal() method now maps to the critical level, as it does in the standard library. Note that the level is discouraged to use there, so we recommend to stick to error() or critical(). #677

• structlog.tracebacks.ExceptionDictTransformer now actually accepts None for locals_max_length and locals_max_string. #675

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Full Changelog →

Credits

structlog is written and maintained by Hynek Schlawack. The idea of bound loggers is inspired by previous work by Jean-Paul Calderone and David Reid.

The development is kindly supported by my employer Variomedia AG, structlog’s Tidelift subscribers, and all my amazing GitHub Sponsors.

The logs-loving beaver logo has been contributed by Lynn Root.