nicegui/website/documentation/content/log_documentation.py

from nicegui import ui

from . import doc


@doc.demo(ui.log)
def main_demo() -> None:
    from datetime import datetime

    log = ui.log(max_lines=10).classes('w-full h-20')
    ui.button('Log time', on_click=lambda: log.push(datetime.now().strftime('%X.%f')[:-5]))


@doc.demo('Attach to a logger', '''
    You can attach a `ui.log` element to a Python logger object so that log messages are pushed to the log element.
    When used inside a page function, it is important to remove the handler when the client disconnects.
    Otherwise, the handler will keep a reference to the log element and the latter will not be garbage collected.
''')
def logger_handler():
    import logging
    from datetime import datetime

    logger = logging.getLogger()

    class LogElementHandler(logging.Handler):
        """A logging handler that emits messages to a log element."""

        def __init__(self, element: ui.log, level: int = logging.NOTSET) -> None:
            self.element = element
            super().__init__(level)

        def emit(self, record: logging.LogRecord) -> None:
            try:
                msg = self.format(record)
                self.element.push(msg)
            except Exception:
                self.handleError(record)

    # @ui.page('/')
    def page():
        log = ui.log(max_lines=10).classes('w-full')
        handler = LogElementHandler(log)
        logger.addHandler(handler)
        ui.context.client.on_disconnect(lambda: logger.removeHandler(handler))
        ui.button('Log time', on_click=lambda: logger.warning(datetime.now().strftime('%X.%f')[:-5]))
    page()  # HIDE


doc.reference(ui.log)