QtLog

Custom Python Log with colored message display for Maya/Houdini/Nuke

PySide6/Python 3.9+

Message Levels

log = get_stream_logger('my_log')

log.info('test info')  # white
log.warning('test warning')  # orange
log.error('test error')  # red
log.critical('test critical')  # purple
log.debug('test debug')  # yellow
log.ok('test ok')  # sky blue
log.file('test file')  # super light blue
log.process('test process')  # light blue
log.done('test done')  # green
log.hint('hint to the user')  # yellow

Usage

Import the logger and create a logger instance, you can create multiple loggers and output them into the same widget.

from qt_log.stream_log import get_stream_logger

log = get_stream_logger('MyToolLog')
log_ext = get_stream_logger('SomeOtherExternalLog')

Import the QtUILogger widget and create an instance of the widget, passing the app, the layout widget and the loggers, a layout widget is required.

from qt_log.qt_ui_logger import QtUILogger

# Inside your app
self.loggers = QtUILogger(
    parent=self,
    layout_widget=self.ui.log_layout,
    loggers=[log, log_ext],
)

Create QtUILogger on the Qt GUI thread after constructing QApplication. The parent must be a QWidget, the destination must be a QLayout, and every logger must be a logging.Logger. Repeated references to the same logger are attached only once.

In your Qt app, you can use QtUILogger to display log messages in a widget.

log.info('Message')
log.warning('Message')
log.error('Message')
log.critical('Message')
log.debug('Message')
log.ok('Message')
log.file('Message')
log.process('Message')
log.done('Message')
log.hint('Message')

Records can be emitted from worker threads. Display updates are queued to the Qt GUI thread, so the widget changes when the Qt event loop processes pending events. Pending display records are bounded at 4,096; under sustained overload, the oldest pending record is discarded. Use self.loggers.dropped_records and self.loggers.peak_pending_records to monitor overload.

When running in Unreal Engine, stream messages are routed through Unreal's native logging API so info, warning, and error records retain their correct Output Log severity. Other hosts continue to use Python's standard logging.StreamHandler.

Lastly, when you close the app, remove the handler from its loggers by overriding closeEvent(). Call the base implementation rather than recursively closing the window.

def closeEvent(self, event):
    """Detach the UI logger before the window is destroyed."""
    self.loggers.close()
    super().closeEvent(event)

Standalone example

Run the host-neutral PySide6 example from the repository root:

uv run python -m example.standalone

The Maya-hosted example remains in example/maya_tool.py and is loaded inside Maya with example.maya_tool.load().

Install

pip install qt-log