Function to attach spdlog to Python logger

[aaron-skydio]

Discussed in #420

^{Originally posted by tchittesh January 9, 2025}
I'm using the python symforce.opt.Optimizer which is printing optimization info

[2025-01-10 01:44:21.428] [info] LM<sym::Optimize> [iter   21] lambda: 4.768e-03, error prev/linear/new: 0.000/0.000/0.000, rel reduction: 0.15934
[2025-01-10 01:44:21.447] [info] LM<sym::Optimize> [iter   22] lambda: 2.384e-03, error prev/linear/new: 0.000/0.000/0.000, rel reduction: 0.19686
[2025-01-10 01:44:21.467] [info] LM<sym::Optimize> [iter   23] lambda: 1.192e-03, error prev/linear/new: 0.000/0.000/0.000, rel reduction: 0.25366

Is there a way to capture this output (generated by spdlog in C++) or redirect it to stdout? Some naive approaches like

from symforce import logger as symforce_logger, LOGGING_FORMAT as SYMFORCE_LOGGING_FORMAT
symforce_logger.handlers.clear()
handler = logging.StreamHandler(sys.stdout)
handler.setLevel(logging.WARNING)
formatter = logging.Formatter(SYMFORCE_LOGGING_FORMAT)
handler.setFormatter(formatter)
symforce_logger.addHandler(handler)

don't seem to work

Conclusion in the discussion was that it would be nice to be able to attach spdlog to the Python logger, which would let us wrap one function to do that (rather than the entire spdlog interface), and then people will be able to manage things through the python logger