Capture traceback in log file

[gpregger-ethz]

Is there a way I can set up the textual logger to either log a traceback to a log file or let my own sys.excepthook handle uncaught exceptions?

I would like to end up with this information in a file:

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[edward-jazzhands]

Yes this is possible, not only that but there's an easy way to do it built right into Rich. Its actually not super well documented, I recall when I figured this out I had to dig through some stuff quite manually. But now I can save you from having to go through the same pain. Here's a working example.

# Python standard lib
from datetime import datetime
# Textual and Rich
from textual.app import App
from textual.widgets import Static, Button
from textual.containers import Container  
from rich.console import Console
from rich.traceback import Traceback


class TextualApp(App[None]):

    CSS = """
    Screen { align: center middle; }
    #my_static { border: solid blue; width: auto;}
    """

    def compose(self):

        with Container(id="my_container"):
            yield Static("Hello, Textual!", id="my_static")
            yield Button("Press me to cause a bug", classes="some-tcss-class")

    def on_button_pressed(self):
        self.query_one("#non_existent_widget")  # This will raise an error

    def _handle_exception(self, error: Exception) -> None:

        self.record_log_files(error)
        super()._handle_exception(error)


    def record_log_files(self, e: Exception):

        with open("error.txt", "w") as log_txt_file:
            console = Console(file=log_txt_file, record=True, width=100)
            console.print(f"Error Report, recorded at: {datetime.now()}\n")
            traceback = Traceback.from_exception(
                type(e),
                e,
                e.__traceback__,
                show_locals=True
            )
            console.print(traceback)            
            console.save_html("error.html")


TextualApp().run()

This will drop an error.txt and error.html file in whatever folder you just ran the script.

[gpregger-ethz]

Very cool, thank you!
I found my log a bit lacking, it seems constructing the traceback like your example doesn't capture a lot of info for me. After some playing around I ended up with this, which gives me pretty much exactly what I see in the terminal during a crash:

def __record_log_files(self, e: Exception):
    with open('crash_log.txt', 'w') as crash_log:
        console = Console(file=crash_log, record=True, width=100)
        console.print(Traceback(show_locals=True, width=256))
        console.save_html('crash_log.html')

A bit unfortunate that App._handle_exception as the key to this doesn't really have much documentation that I could find...

[edward-jazzhands]

App._handle_exception doesn't have documentation because its a private method. Not sure if you're very familiar with Python in general but every time you see a leading underscore in front of a method, that means its private. So its meant for internal usage within the framework and not intended to be documented, or used by anyone else. When you're good at Python you learn that these can be overridden to provide custom behavior. It's essentially the framework or program saying this is not meant to be used and they take no responsibility if you decide to override it.