anti1869 · December 21, 2015 19:28 · Dec 21, 2015
diff --git a/parallel-script.py b/parallel-script.py
@@ -0,0 +1,98 @@
+#!/usr/bin/env python
+
+"""
+Test parallel scripts running with asyncio executors.
+
+Requires at least Python 3.4 to run.
+"""
+
+import asyncio
+import os
+import subprocess
+from functools import partial
+from typing import Sequence, Any
+
+from asyncio import async as ensure_future  # async is deprecated in Python 3.4
+
+
+COMMANDS = [
+    "ls /usr",
+    "ls /usr/local",
+    "ls ~",
+    "ls /themiddleofnowhere",
+]
+
+MAX_RUNNERS = 2
+
+semaphore = asyncio.Semaphore(MAX_RUNNERS)
+
+
+def run_command(cmd: str) -> str:
+    """
+    Run prepared behave command in shell and return its output.
+
+    :param cmd: Well-formed behave command to run.
+    :return: Command output as string.
+    """
+
+    try:
+        output = subprocess.check_output(
+            cmd,
+            stderr=subprocess.STDOUT,
+            universal_newlines=True,
+            shell=True,
+            cwd=os.getcwd(),
+        )
+
+    except subprocess.CalledProcessError as e:
+        output = e.output
+
+    return output
+
+
+@asyncio.coroutine
+def run_command_on_loop(loop: asyncio.AbstractEventLoop, command: str) -> bool:
+    """
+    Run test for one particular feature, check its result and return report.
+
+    :param loop: Loop to use.
+    :param command: Command to run.
+    :return: Result of the command.
+    """
+    with (yield from semaphore):
+        runner = partial(run_command, command)
+        output = yield from loop.run_in_executor(None, runner)
+        yield from asyncio.sleep(2)  # Slowing a bit for demonstration purposes
+        return output
+
+
+@asyncio.coroutine
+def run_all_commands(command_list: Sequence[str] = COMMANDS) -> None:
+    """
+    Run all commands in a list
+
+    :param command_list: List of commands to run.
+    """
+    loop = asyncio.get_event_loop()
+    fs = [run_command_on_loop(loop, command) for command in command_list]
+    for f in asyncio.as_completed(fs):
+        result = yield from f
+        ensure_future(process_result(result))
+
+
+@asyncio.coroutine
+def process_result(result: Any):
+    """
+    Do something useful with result of the commands
+    """
+    print(result)
+
+
+def main() -> None:
+    """ Entry point """
+    loop = asyncio.get_event_loop()
+    loop.run_until_complete(run_all_commands())
+
+
+if __name__ == "__main__":
+    main()
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