On Sat, Jun 6, 2020 at 6:46 AM Steven D'Aprano <st...@pearwood.info> wrote:
> I think the first thing that needs to be done, before creating a bpo > issue, is to get consensus that it's both a plausible idea and a good > idea, and I don't think that the discussion did either. > > Discussion starts here: > > > https://mail.python.org/archives/list/python-ideas@python.org/thread/I74LVJWJLE2LUCCZGOF5A5JDSDHJ6WX2/#BVUMURTEZFQG36HRCZYRSWJK6OTZIBZG I was also under the impression that a new thread had been started, since that's what it looks like in my inbox, but everything is actually under that link already. Mailman is confusing. > Bar's initial reason for this: > > "Will be useful mostly for debugging purposes instead of temporarily > modifying the code." > > Okay, but how does that work? I have a script: > > # myscript.py > print("Hello world") > > and I want to add logging to it. So I set the environment variable, or > use the proposed -L command line switch, and call the script: > > PYTHONLOGGING=mylogfile python myscript.py > > but what exactly gets logged? > I'm assuming you made a small mistake here, because `PYTHONLOGGING` would take a log level, not a filename. > It's one thing to say that the interpreter takes care of importing > logging and setting up a basic logger, and that's great, but I still > have to import logging and call the `logging.info(...)` functions, > so what does this proposal give us, *in detail* please, and how do I use > it? > My understanding is that it does something like: ``` import logging import os logging.basicConfig(level=os.environ["PYTHONLOGGING"]) ``` and that this is useful if you're using a library that uses logging, i.e. ` logging.info(...)` calls have already been written for you, you just want an easy way to activate them. I've read the entire thread and there is lot of detail there that seems > to be written for expert users of logging. If you're an expert user of > logging, you probably don't need an environment variable, or you can > handle it yourself with os.environ.get('LOGLEVEL'). > > How is this going to impact basic and intermediate users of logging? > I think for users familiar with environment variables, `PYTHONLOGGING=INFO python myscript.py` might be easier to remember than `import logging; logging.basicConfig(level='INFO')`. On the other hand, the Python code is fairly discoverable in an IDE. `import log` autocompletes `logging` for me, `logging.config` autocompletes `logging.basicConfig`, and from there it's easy to see the docstring and parameters. And adding more ways of doing things can make learning harder. > The tutorial warns: "As [logging.basicConfig] is intended as a one-off > simple configuration facility, only the first call will actually do > anything: subsequent calls are effectively no-ops." > > So what happens if I have a script that explicitly calls basicConfig but > I accidentally run it with the -L switch or PYTHONLOGGING? > > E.g. I may have an alias 'python=python -L', or I may have set the > environment variable in a shell and then forgotten it. I sometimes have > shells open for weeks at a time, I'm going to be terribly confused if > myscript logs correctly in one open shell but not in another because of > an environment variable I set two weeks earlier. > I think this last point is interesting, and puts me in favour of explicit calls to basicConfig overriding the environment variable, so the environment variable wouldn't be *exactly* equivalent to a call to basicConfig.
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