Widget log handler

[tdamsma]

I would like to have a widget that I can use on e.g. a debug screen that works with the python logger. So the result is logs are written in the app itself (and not to an extra instance of the textual console). After some fiddling around, I think I came up with something workable. So I am basically answering my own question, but perhaps this is useful, or there is a better way or this can be included in a less hacky way.

The main idea is to leverage the RichLog as Widget, and the RichHandler as log handler. The hack is that the RichHandler.console is replaced by the RichLog, like so:

class LoggingConsole(RichLog):
    file = False
    console: Widget

    def print(self, content):
        self.write(content)
logger = logging.getLogger(__name__)
logger.addHandler(RichHandler(console=LoggingConsole()))

No when used in an app, everything logger using the logging module is shown in the logging widget:

import logging

from rich.logging import RichHandler
from textual.app import App, ComposeResult
from textual.widget import Widget
from textual.widgets import Button, Label, RichLog, Welcome


class LoggingConsole(RichLog):
    file = False
    console: Widget

    def print(self, content):
        self.write(content)


logger = logging.getLogger(__name__)
rich_log_handler = RichHandler(
    console=LoggingConsole(),  # type: ignore
    rich_tracebacks=True,
)
logger.addHandler(rich_log_handler)
logger.setLevel(logging.DEBUG)


class QuestionApp(App[str]):
    def compose(self) -> ComposeResult:
        yield Label("Do you love Textual?")
        yield Button("Yes", id="yes", variant="primary")
        yield Button("No", id="no", variant="error")
        yield rich_log_handler.console  # type: ignore

    def on_button_pressed(self, event: Button.Pressed) -> None:
        logger.info("Button pressed")
        logger.debug(event)
        if event.button.id == "no":
            try:
                assert "no" == "yes"
            except AssertionError:
                logger.exception("Assertion error")


if __name__ == "__main__":
    app = QuestionApp()
    reply = app.run()
    print(reply)

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[willmcgugan]

It clearly works! It's clever, but a bit of a hack. Can't promise it won't fail because of missing methods.

It would be a little more work, but you could build a logging handler that writes to a given log widget. A good starting point would be Textual's logging handler which could be extended to also write to a widget.

[etabor20]

Leaving this here in case anyone finds it useful - I used this logging trick in a project and kept getting logs bleeding through the app because they were still being written to the default stdout - to prevent these message duplications just add logger.propagate = False so they only get sent to the specified handler.

Thanks for the great library!