worker.py

#!/usr/bin/env python3
#
#  Podcasts Export
#  ---------------
#  Douglas Watson, 2022, MIT License
#
#  worker.py: boilerplate to create background tasks that communicate back with 
#             main thread.

import sys
import traceback

from PySide6.QtCore import QObject, Signal, QRunnable, Slot

class WorkerSignals(QObject):
    '''
    Defines the signals available from a running worker thread.

    Supported signals are:

    finished
        No data

    error
        tuple (exctype, value, traceback.format_exc() )

    result
        object data returned from processing, anything

    progress
        [0, 100] percentage execution of task, for progress bars.

    '''
    finished = Signal()  # QtCore.Signal
    error = Signal(tuple)
    result = Signal(object)
    progress = Signal(float)
    status = Signal(int)
    message = Signal(str)


class Worker(QRunnable):
    '''
    Worker thread

    Inherits from QRunnable to handler worker thread setup, signals and wrap-up.

    :param callback: The function callback to run on this worker thread. Supplied args and
                     kwargs will be passed through to the runner.
    :type callback: function
    :param args: Arguments to pass to the callback function
    :param kwargs: Keywords to pass to the callback function

    '''

    def __init__(self, fn, *args, **kwargs):
        super(Worker, self).__init__()
        # Store constructor arguments (re-used for processing)
        self.fn = fn
        self.args = args
        self.kwargs = kwargs
        self.signals = WorkerSignals()

    @Slot()  # QtCore.Slot
    def run(self):
        '''
        Initialise the runner function with passed args, kwargs.
        '''

        # Retrieve args/kwargs here; and fire processing using them
        try:
            result = self.fn(
                *self.args, **self.kwargs,
                set_progress=self.signals.progress.emit,
                emit_message=self.signals.message.emit,
            )
        except:
            traceback.print_exc()
            exctype, value = sys.exc_info()[:2]
            self.signals.error.emit((exctype, value, traceback.format_exc()))
        else:
            self.signals.result.emit(result)  # Return the result of the processing
        finally:
            self.signals.finished.emit()  # Done