Error dialog

In plain words

A window that pops up when something fails, saying what went wrong and where, with a button to copy it for a bug report.

ui.error_dialog(info, on_close) shows an error in a dialog: its message, where it happened, the file and line it comes from and the traceback in a read-only editor, where any part can be selected and copied. Its buttons copy the whole report, go to the origin (on_go_to, labeled go_to_label), show it among the logs (on_logs) and close. more adds a line saying how many other errors came after it. info is a ui.ErrorInfo; show the dialog with a Dialog layer.

ui.error_dialog · Category: Dialogs · Full reference →

Preview

Code

def average(values):
    return sum(values) / len(values)

try:
    average([])
except ZeroDivisionError as err:
    info = ui.ErrorInfo.from_exception(err, where="Totals")

ui.dialog_layer(main_view(), ui.error_dialog(info, on_close, on_go_to=on_go_to, on_logs=on_logs, width=620))

New

This component was added recently. Tell us how it works for you in the issue tracker.

When to use

• When something the user asked for fails (saving, exporting, running a script) and the details matter.
• From the Details button of an Error boundary.
• For a short message without a traceback, use an Alert with kind="error".

Usage

import pyzed as pz
from pyzed import ui

class Notes(pz.App):
    def __init__(self):
        self.error = None

    def save(self):
        try:
            write_notes(self.notes)
        except OSError as err:
            self.error = ui.ErrorInfo.from_exception(err, where="Save")

    def close_error(self):
        self.error = None

    def view(self):
        dialog = ui.error_dialog(self.error, self.close_error) if self.error else None
        return ui.dialog_layer(self.page(), dialog, on_dismiss=self.close_error)

Variants

About these captures

Each capture is recorded by pyzed itself, off-screen at 2x, in One Dark or One Light to match this site’s theme, and cropped to the component so it shows at its real size. The pointer hovers, presses or types into it; a component that does not react to the pointer cycles through a few themes. With reduced motion you see the first frame. Open Code under a capture to see the snippet that draws it; free names such as on_save stand for your own callbacks.

Options

Without a traceback the dialog leaves out the code box, as with an ErrorInfo you build yourself.

Close only

Code

def average(values):
    return sum(values) / len(values)

try:
    average([])
except ZeroDivisionError as err:
    info = ui.ErrorInfo.from_exception(err, where="Totals")

ui.error_dialog(info, on_close, width=480)

on_go_to=, go_to_label=

Code

def average(values):
    return sum(values) / len(values)

try:
    average([])
except ZeroDivisionError as err:
    info = ui.ErrorInfo.from_exception(err, where="Totals")

ui.error_dialog(info, on_close, on_go_to=on_go_to, go_to_label="Open app.py",
                width=480)

on_logs=

Code

def average(values):
    return sum(values) / len(values)

try:
    average([])
except ZeroDivisionError as err:
    info = ui.ErrorInfo.from_exception(err, where="Totals")

ui.error_dialog(info, on_close, on_logs=on_logs, width=480)

more=2

Code

def average(values):
    return sum(values) / len(values)

try:
    average([])
except ZeroDivisionError as err:
    info = ui.ErrorInfo.from_exception(err, where="Totals")

ui.error_dialog(info, on_close, more=2, width=480)

title=

Code

def average(values):
    return sum(values) / len(values)

try:
    average([])
except ZeroDivisionError as err:
    info = ui.ErrorInfo.from_exception(err, where="Totals")

ui.error_dialog(info, on_close, title="The totals could not be computed", width=480)

No traceback

Code

info = ui.ErrorInfo("PermissionError", "[Errno 13] Permission denied: 'notes.md'", where="Save")
ui.error_dialog(info, on_close, width=480)

Events

Error dialog has 3 events of its own, listed below. Like every widget it also has the 18 common events (click, double_click, right_click, mouse_enter, drag, key_down, resize…), attached with .on(...): see Events and Events of every component.

Event	Handler gets	When
on_close	()	Close button and Escape.
on_go_to	()	Adds the go-to button (open the file at the line).
on_logs	()	Adds a Show in Logs button.

Handler gets is what Pyzed passes to your callable: () means nothing. Any handler can also be a message (a value that is not callable), which goes to update().

Handling the events

The same events written three ways. Imperative: methods of the app change self. Declarative: the handlers produce messages and one update() decides. Functional: a pure function draws an immutable state and asks for changes with set_state(...). See Imperative, declarative and functional.

Imperative

class Notes(pz.App):
    def __init__(self):
        try:
            open("/no/such/file")
        except OSError as err:
            self.error = ui.ErrorInfo.from_exception(err, where="Open")

    def close(self):                     # on_close: the button and Escape
        self.error = None

    def view(self):
        dialog = ui.error_dialog(self.error, self.close,
                                 on_go_to=lambda: print("go to", self.error.origin),  # adds Go to
                                 on_logs=lambda: print("show logs")) if self.error else None
        return ui.dialog_layer(main_view(), dialog, on_dismiss=self.close)

Declarative

class Notes(pz.App):
    error = ui.ErrorInfo("FileNotFoundError", "No such file: notes.txt")

    def update(self, message):
        match message:
            case "close":
                self.error = None
            case "logs":
                print("show logs")

    def view(self):
        dialog = ui.error_dialog(self.error, "close", on_logs="logs") if self.error else None
        return ui.dialog_layer(main_view(), dialog, on_dismiss="close")

Functional

from dataclasses import dataclass


@dataclass(frozen=True)
class State:
    error: object = ui.ErrorInfo("FileNotFoundError", "No such file: notes.txt")


def view(state, set_state):
    close = lambda: set_state(error=None)
    dialog = ui.error_dialog(state.error, close) if state.error else None
    return ui.dialog_layer(main_view(), dialog, on_dismiss=close)

Tips

Tip

on_go_to receives no arguments: read the file and line from info.origin (a (path, line) pair, or None) and open it there. The traceback box is a read-only editor, so the user can select a single line and copy it, while Copy error copies info.report().

Properties and API

ui.error_dialog

error_dialog(
    info,
    on_close,
    *,
    title=None,
    on_go_to=None,
    go_to_label=None,
    on_logs=None,
    more=0,
    width=680,
    theme=None,
)

A dialog with an error: its message, where it happened, the file and line it comes from and the traceback in a read-only editor (select and copy any part), with buttons to copy everything, go to the origin, see it among the logs and close. Show it with ui.dialog_layer or ui.layer.

Property	Default	Description
info	required	A ui.ErrorInfo.
title	None	Heading (“Something went wrong”).
go_to_label	None	Its text (“Go to source”).
more	0	How many other errors came after it (a line says so).
width	680	Width in pixels or a modal size.
theme	None	Theme override.

Events: on_close, on_go_to, on_logs (events).

Full reference →

Related

Error boundaryDraws a part of the view, or an error card in its place when it fails.

AlertA message with one button.

Dialog layerCenters a dialog over your view with a dimmed backdrop.

ModalA dialog surface with title, content and footer buttons.