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A live, auto-scrolling two-column log in a split pane

Keywords: split view · log · streaming · history · layout

Builds a vertical ~pytanga.viz.SplitView with a ~pytanga.viz.ButtonView pane and a ~pytanga.viz.LogView pane. The button appends lines (a plain string and a structured dict) via log_view.log, which pushes log_update to the browser; the log auto-scrolls to the newest line, alternates row shading, and keeps only the last max_history entries. The timestamp column shows local time with microseconds by default; the date and the local UTC offset are opt-in via show_date / show_utc_offset.

Run

uv run python py/examples/viz/ui/static/log_view.py

Source

viz/ui/static/log_view.py

Code

# SPDX-License-Identifier: Apache-2.0
# Copyright 2021 Christian Perwass

"""log_view.py — A live, auto-scrolling two-column log in a split pane.

Builds a vertical :class:`~pytanga.viz.SplitView` with a
:class:`~pytanga.viz.ButtonView` pane and a :class:`~pytanga.viz.LogView` pane.
The button appends lines (a plain string and a structured dict) via
``log_view.log``, which pushes ``log_update`` to the browser; the log
auto-scrolls to the newest line, alternates row shading, and keeps only the
last ``max_history`` entries.  The timestamp column shows local time with
microseconds by default; the date and the local UTC offset are opt-in via
``show_date`` / ``show_utc_offset``.

Run with:  uv run python py/examples/viz/ui/static/log_view.py

Keywords: split view, log, streaming, history, layout
"""

from typing import Any

from itertools import count

from pytanga.viz import ButtonView, ControlEvent, LogView, Size, SplitView, Visualizer

viz = Visualizer(reuse_existing=False, title="Tanga — Live Log")

# Timestamps show local time + microseconds by default; opt into the date and
# the local UTC offset via show_date / show_utc_offset.
log = LogView(id="log", max_history=100, show_date=True, show_utc_offset=True)
log.log("Log view ready.")
log.log({"message": "structured line", "level": "info"})

# The full data API: `log.get_log()` -> list[dict], `log.write_file(path)`,
# `log.load_file(path)`, and `log.clear()`.
_counter = count()


async def on_append(_value: Any, _event: ControlEvent) -> None:
    n = next(_counter)
    log.log(f"Appended line #{n}")
    log.log({"message": "structured event", "step": n, "level": "warn"})


layout = SplitView(
    orientation="vertical",
    sizes=[Size.percent(15), Size.percent(85)],
    children=[
        ButtonView("btn_append", label="Append lines", on_click=on_append),
        log,
    ],
)

viz.show(layout=layout)
print("Click the button to append live log lines. Press Ctrl+C to exit.")
viz.wait()