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  • Re: Ref-strings in logging messages (was: Performance issue with CPytho

    From Skip Montanaro@21:1/5 to All on Fri Oct 7 11:03:08 2022
    Dang autocorrect. Subject first word was supposed to be "f-strings" not "ref-strings." Sorry about that.

    S

    On Fri, Oct 7, 2022, 10:45 AM Skip Montanaro <skip.montanaro@gmail.com>
    wrote:



    On Fri, Oct 7, 2022 at 9:42 AM Andreas Ames <andreas.0815.qwertz@gmail.com> wrote:

    1. The culprit was me. As lazy as I am, I have used f-strings all over the >> place in calls to `logging.logger.debug()` and friends, evaluating all
    arguments regardless of whether the logger was enabled or not.


    I thought there was some discussion about whether and how to efficiently admit f-strings to the logging package. I'm guessing that's not gone
    anywhere (yet).

    Skip


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  • From Barry@21:1/5 to All on Fri Oct 7 18:04:33 2022
    On 7 Oct 2022, at 16:48, Skip Montanaro <skip.montanaro@gmail.com> wrote:

    On Fri, Oct 7, 2022 at 9:42 AM Andreas Ames <andreas.0815.qwertz@gmail.com>
    wrote:

    1. The culprit was me. As lazy as I am, I have used f-strings all over the >> place in calls to `logging.logger.debug()` and friends, evaluating all
    arguments regardless of whether the logger was enabled or not.


    I thought there was some discussion about whether and how to efficiently admit f-strings to the logging package. I'm guessing that's not gone
    anywhere (yet).

    That cannot be done as the f-string is computed before the log call.

    Maybe you are thinking of the lazy expression idea for this. That idea
    seems to have got no where as its not clear how to implement it without performance issues.

    Barry


    Skip
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  • From MRAB@21:1/5 to Skip Montanaro on Fri Oct 7 18:10:33 2022
    On 2022-10-07 16:45, Skip Montanaro wrote:
    On Fri, Oct 7, 2022 at 9:42 AM Andreas Ames <andreas.0815.qwertz@gmail.com> wrote:

    1. The culprit was me. As lazy as I am, I have used f-strings all over the >> place in calls to `logging.logger.debug()` and friends, evaluating all
    arguments regardless of whether the logger was enabled or not.


    I thought there was some discussion about whether and how to efficiently admit f-strings to the logging package. I'm guessing that's not gone
    anywhere (yet).

    Letting you pass in a callable to call might help because that you could
    use lambda.

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  • From Weatherby,Gerard@21:1/5 to All on Fri Oct 7 17:55:13 2022
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  • From Barry@21:1/5 to All on Fri Oct 7 18:28:06 2022
    On 7 Oct 2022, at 18:16, MRAB <python@mrabarnett.plus.com> wrote:

    On 2022-10-07 16:45, Skip Montanaro wrote:
    On Fri, Oct 7, 2022 at 9:42 AM Andreas Ames <andreas.0815.qwertz@gmail.com> >>> wrote:
    1. The culprit was me. As lazy as I am, I have used f-strings all over the >>> place in calls to `logging.logger.debug()` and friends, evaluating all
    arguments regardless of whether the logger was enabled or not.

    I thought there was some discussion about whether and how to efficiently
    admit f-strings to the logging package. I'm guessing that's not gone
    anywhere (yet).
    Letting you pass in a callable to call might help because that you could use lambda.

    Yep, that’s the obvious way to avoid expensive log data generation.
    Would need logging module to support that use case.

    Barry

    --
    https://mail.python.org/mailman/listinfo/python-list


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  • From Julian Smith@21:1/5 to Barry on Fri Oct 7 21:12:42 2022
    On Fri, 7 Oct 2022 18:28:06 +0100
    Barry <barry@barrys-emacs.org> wrote:

    On 7 Oct 2022, at 18:16, MRAB <python@mrabarnett.plus.com> wrote:

    On 2022-10-07 16:45, Skip Montanaro wrote:
    On Fri, Oct 7, 2022 at 9:42 AM Andreas Ames <andreas.0815.qwertz@gmail.com>
    wrote:
    1. The culprit was me. As lazy as I am, I have used f-strings all over the
    place in calls to `logging.logger.debug()` and friends, evaluating all >>> arguments regardless of whether the logger was enabled or not.

    I thought there was some discussion about whether and how to efficiently >> admit f-strings to the logging package. I'm guessing that's not gone
    anywhere (yet).
    Letting you pass in a callable to call might help because that you could use lambda.

    Yep, that’s the obvious way to avoid expensive log data generation.
    Would need logging module to support that use case.

    I have some logging code that uses eval() to evaluate expressions using
    locals and globals in a parent stack frame, together with a parser to
    find `{...}` items in a string.

    I guess this constitutes a (basic) runtime implementation of f-strings.
    As such it can avoid expensive evaluation/parsing when disabled, though
    it's probably slow when enabled compared to native f-strings. It seems
    to work quite well in practise, and also allows one to add some extra formatting features.

    For details see:

    https://git.ghostscript.com/?p=mupdf.git;a=blob;f=scripts/jlib.py;h=e85e9f2c4;hb=HEAD#l41

    - Jules

    --
    http://op59.net

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  • From Barry@21:1/5 to All on Fri Oct 7 22:15:17 2022
    On 7 Oct 2022, at 19:09, Weatherby,Gerard <gweatherby@uchc.edu> wrote:
    The obvious way to avoid log generation is:

    if logger.isEnableFor(logging.DEBUG):
    logger.debug( expensive processing )


    Of course, having logging alter program flow could lead to hard to debug bugs.

    Altered flow is less of an issue the the verbosity of the above.
    We discussed ways to improve this pattern a few years ago.
    That lead to no changes.

    What I have used is a class that defines __bool__ to report if logging is enabled and __call__ to log. Then you can do this:

    log_debug = logger_from(DEBUG)

    log_debug and log_debug(‘expensive %s’ % (complex(),))

    Barry


    From: Python-list <python-list-bounces+gweatherby=uchc.edu@python.org> on behalf of Barry <barry@barrys-emacs.org>
    Date: Friday, October 7, 2022 at 1:30 PM
    To: MRAB <python@mrabarnett.plus.com>
    Cc: python-list@python.org <python-list@python.org>
    Subject: Re: Ref-strings in logging messages (was: Performance issue with CPython 3.10 + Cython)
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    On 7 Oct 2022, at 18:16, MRAB <python@mrabarnett.plus.com> wrote:

    On 2022-10-07 16:45, Skip Montanaro wrote:
    On Fri, Oct 7, 2022 at 9:42 AM Andreas Ames <andreas.0815.qwertz@gmail.com>
    wrote:
    1. The culprit was me. As lazy as I am, I have used f-strings all over the >>>> place in calls to `logging.logger.debug()` and friends, evaluating all >>>> arguments regardless of whether the logger was enabled or not.
    I thought there was some discussion about whether and how to efficiently >>> admit f-strings to the logging package. I'm guessing that's not gone
    anywhere (yet).
    Letting you pass in a callable to call might help because that you could use lambda.

    Yep, that’s the obvious way to avoid expensive log data generation.
    Would need logging module to support that use case.

    Barry

    --
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  • From Weatherby,Gerard@21:1/5 to All on Sat Oct 8 10:50:51 2022
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  • From Barry Scott@21:1/5 to All on Mon Oct 24 21:52:12 2022
    On 8 Oct 2022, at 11:50, Weatherby,Gerard <gweatherby@uchc.edu> wrote:

    Logging does support passing a callable, if indirectly. It only calls __str__ on the object passed if debugging is enabled.

    class Defer:

    def __init__(self,fn):
    self.fn = fn

    def __str__(self):
    return self.fn()

    def some_expensive_function():
    return "hello"

    logging.basicConfig()
    logging.debug(Defer(some_expensive_function))

    Oh what a clever hack. Took a few minutes of code reading to see why this works.
    You are exploiting the str(msg) that is in class LogRecords getMessage().

    ```
    def getMessage(self):
    """
    Return the message for this LogRecord.

    Return the message for this LogRecord after merging any user-supplied
    arguments with the message.
    """
    msg = str(self.msg)
    if self.args:
    msg = msg % self.args
    return msg
    ```

    Barry




    From: Python-list <python-list-bounces+gweatherby=uchc.edu@python.org <mailto:python-list-bounces+gweatherby=uchc.edu@python.org>> on behalf of Barry <barry@barrys-emacs.org <mailto:barry@barrys-emacs.org>>
    Date: Friday, October 7, 2022 at 1:30 PM
    To: MRAB <python@mrabarnett.plus.com <mailto:python@mrabarnett.plus.com>>
    Cc: python-list@python.org <mailto:python-list@python.org> <python-list@python.org <mailto:python-list@python.org>>
    Subject: Re: Ref-strings in logging messages (was: Performance issue with CPython 3.10 + Cython)

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    On 7 Oct 2022, at 18:16, MRAB <python@mrabarnett.plus.com> wrote:

    On 2022-10-07 16:45, Skip Montanaro wrote:
    On Fri, Oct 7, 2022 at 9:42 AM Andreas Ames <andreas.0815.qwertz@gmail.com>
    wrote:
    1. The culprit was me. As lazy as I am, I have used f-strings all over the
    place in calls to `logging.logger.debug()` and friends, evaluating all >>> arguments regardless of whether the logger was enabled or not.

    I thought there was some discussion about whether and how to efficiently >> admit f-strings to the logging package. I'm guessing that's not gone
    anywhere (yet).
    Letting you pass in a callable to call might help because that you could use lambda.

    Yep, that’s the obvious way to avoid expensive log data generation.
    Would need logging module to support that use case.

    Barry

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