Adding Formatter and example including timestamp

[FoamyGuy]

This is intended to supersede #51.

This adds support for a subset of functionality of Formatters (https://docs.python.org/3/library/logging.html#formatter-objects) to be created and set on Handlers.

A new example is provided that illustrates the usage of a few different Formatters including one that use {asctime}.

The output of this example when run in cpython with the cpython logging import used:

Default formatter example
2024-08-05 18:18:37,448 INFO: Timestamp formatter example
192.168.1.188 INFO: Custom formatter example

The output of this example when run in cpython with adafruit_logging import used:

Default formatter example

2024-08-05 18:19:19 INFO: Timestamp formatter example

192.168.1.188 INFO: Custom formatter example

The output of this example when run in circuitpython on a Feather S2 9.1.1

Default formatter example

2000-01-01 02:32:47 INFO: Timestamp formatter example

192.168.1.188 INFO: Custom formatter example

The Formatter init function signature matches the CPython version, but at this time not all of the functionality is implemented so some of the arguments are ignored.

The arguments currently supported are:

• fmt for the custom format string
• defaults for a dictionary containing arbitrary extra values that can be included in the format string
• style this implementation only supports '{'

In CPython the default value for sytle is '%' but in this implementation have changed it to '{' because I didn't implement support for the percent style. The code for supporting curly brackets was minimal as it was able to leverage string.format(). I do not know if there is some simpler way to format strings with the percent format like '%(message)s but the only way I know of would involve regex and be somewhat complex. If anyone knows a simple way to do that I'd be willing to add it and switch the default over to '%' so that we can match the CPython implementation.

I've noticed that adafruit_logging seems to include extra empty lines in between the printed log messages (as depicted in sample output above). I'm not certain of the root cause of that, but I believe it's unrelated to this PR and could be fixed seperately. I tested the currently released version of this library on both CPython and Circuitpython and see the extra spaces appearing in both cases. (edit: #62 provides a solution for the extra lines.)

[FoamyGuy]

The only other current difference in behavior between this implementation and the cpython logging one is that in cpython logging {asctime} includes a comma and another value after the seconds. e.g.

18:18:37,448

But in circuitpython time.localtime() doesn't have any units smaller than seconds so that comma and fractional part are omitted:

18:19:19

[FoamyGuy]

Converting to draft. With help for elpekenin on discord I've learned about this syntax for percent formatting: "%(name)s" % {"name": "hello"}

That was a piece missing in my knowledge of python. With this syntax it should be fairly easy to make the '%' style functionality work correctly and then switch the default value to % in order to fully match the CPython API.

Will un-draft this after I make that change.

[FoamyGuy]

I think this is ready for another look now.

The latest commits have implemented the '%' style and changed the default to use that (matching CPython).

I updated the new example to illustrate usage of both supported styles.

I re-tested the latest version successfully on a Feather S2 TFT 9.1.1 and running under CPython both with adafruit_logging and the cpython built-in logging, all appear to me to output the expected results.

[tannewt]

This looks great! Thanks for matching CPython. One question about defaults.

[tannewt]

Thank you!