Add GUI example

Author: TheGreatCabbage

examples/gui/gui.py

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+#  MIT License
+#
+#  Copyright (c) 2019 Sam McCormack
+#
+#  Permission is hereby granted, free of charge, to any person obtaining a copy
+#  of this software and associated documentation files (the "Software"), to deal
+#  in the Software without restriction, including without limitation the rights
+#  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+#  copies of the Software, and to permit persons to whom the Software is
+#  furnished to do so, subject to the following conditions:
+#
+#  The above copyright notice and this permission notice shall be included in all
+#  copies or substantial portions of the Software.
+#
+#  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+#  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+#  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+#  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+#  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+#  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+#  SOFTWARE.
+
+"""
+Demonstrates the usage of Scheduler in a simple PyQt program, which shows progress and output.
+
+Dependencies are in `requirements.txt`. To install them, run `pip install -r requirements.txt --user`.
+"""
+
+import asyncio
+import random
+import sys
+import time
+from multiprocessing import Queue, Process
+from typing import List, Tuple
+
+import asyncqt
+from PyQt5 import QtGui
+from PyQt5.QtWidgets import QApplication, QLabel, QProgressBar, QVBoxLayout, QWidget, QPushButton
+
+from scheduler.Scheduler import Scheduler
+
+
+def long_calculation(queue: Queue, sleep_time: int) -> None:
+    """
+    Will be executed in another process. Simulates a long calculation,
+    and puts the 'result' in the queue.
+    """
+    time.sleep(sleep_time)
+    queue.put((sleep_time,))
+
+
+class Window(QWidget):
+    """Basic Window class."""
+
+    def __init__(self):
+        super().__init__()
+
+        layout = QVBoxLayout()
+        self.setLayout(layout)
+
+        self.label = QLabel("Output from processes will be shown here", self)
+        layout.addWidget(self.label)
+
+        self.progress = QProgressBar(self)
+        layout.addWidget(self.progress)
+
+        self.button = QPushButton("Start", self)
+        self.button.clicked.connect(self.on_click)
+        layout.addWidget(self.button)
+
+        self.scheduler: Scheduler = None
+
+    def on_click(self):
+        """Called when the button is clicked."""
+        if self.scheduler is None or not self.scheduler.is_running():
+            # "Start" was clicked. Start the coroutine which runs the scheduler.
+            asyncio.ensure_future(self.do_calculations())
+            self.button.setText("Cancel")
+        else:
+            # "Cancel" was clicked. Terminate the scheduler.
+            self.scheduler.terminate()
+            self.button.setText("Start")
+            self.progress.setValue(0)
+
+    async def do_calculations(self):
+        """Does the calculations using a scheduler, and shows the output in the label."""
+        self.scheduler = Scheduler(progress_callback=self.on_progress)
+
+        num_processes = 16
+        for i in range(num_processes):
+            # Generate random input for function.
+            sleep = random.randint(1, 8)
+
+            queue = Queue()
+            process = Process(target=long_calculation, args=(queue, sleep,))
+            self.scheduler.add(process, queue)
+
+        # Run all processes and `await` the results: an ordered list containing one tuple from each process.
+        output: List[Tuple] = await self.scheduler.run()
+
+        # If the scheduler was terminated before completion, we don't want the results.
+        if not self.scheduler.terminated:
+            text = ", ".join([str(i[0]) for i in output])
+            self.label.setText(f"Output: {text}")
+            self.button.setText("Start")
+
+    def on_progress(self, done: int, total: int) -> None:
+        """Updates the progress bar when scheduler finishes a task."""
+        if done == 0:
+            self.progress.setMaximum(total)
+        self.progress.setValue(done)
+
+    def closeEvent(self, event: QtGui.QCloseEvent) -> None:
+        """Terminates the scheduler when the window exits."""
+        if self.scheduler:
+            self.scheduler.terminate()
+
+
+if __name__ == "__main__":
+    app = QApplication(sys.argv)
+
+    # Important: set the event loop using `asyncqt`.
+    loop = asyncqt.QEventLoop(app)
+    asyncio.set_event_loop(loop)
+
+    window = Window()
+    window.show()
+
+    app.exec()

examples/gui/requirements.txt

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+PyQt5
+asyncqt