update concurrency examples

concurrency/async_fibonacci.py

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+"""
+Example of parallel execution with asyncio
+
+see:
+https://docs.python.org/3/library/asyncio-task.html
+"""
+import asyncio
+import random
+from functools import reduce
+
+
+def multiply(a, b):
+    return a * b
+
+
+async def factorial(number):
+    """delayed calculation of fibonacci number"""
+    result = reduce(multiply, range(1, number + 1), 1)
+    delay = random.randint(5, 20)
+    await asyncio.sleep(delay)
+    print(f"after {delay:2} seconds: {number}! = {result}")
+
+
+async def main():
+    # create concurrent tasks
+    tasks = []
+    for i in range(10):
+        tasks.append(asyncio.create_task(factorial(i)))
+
+    # wait for tasks to finish
+    # (all have to be awaited)
+    for t in tasks:
+        await t
+
+
+# run the toplevel async function
+asyncio.run(main())

concurrency/fibonacci.py

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+import sys
+import time
+import random
+
+n = int(sys.argv[1])
+result = 1
+
+while n > 0:
+    result *= n
+    n -= 1
+
+delay = random.randint(5, 15)
+time.sleep(delay)
+print(f"fibonacci of {sys.argv[1]} = {result} after {delay} sec")

concurrency/subprocess_fibonacci.py

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+"""
+Launch processes with the subprocess module
+
+https://docs.python.org/3/library/subprocess.html
+"""
+
+import subprocess
+
+# launch a single external process
+# r = subprocess.run(["python", "fibonacci.py", str(5)])
+# try some other command than Python
+
+
+procs = []
+for i in range(10):
+    cmd = ["python", "fibonacci.py", str(i)]
+    p = subprocess.Popen(cmd) # , stdout=subprocess.PIPE)
+    # add stdout argument to see results immediately
+    procs.append(p)
+
+for p in procs:
+    p.wait()
+    # read output from pipe
+    #print(p.stdout.read().encode())

concurrency/thread_fibonacci.py

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+"""
+Fibonacci with threads
+# adopted from
+http://www.devshed.com/c/a/Python/Basic-Threading-in-Python/1/
+"""
+
+import threading
+import time
+import random
+
+
+class FibonacciThread(threading.Thread):
+    def __init__(self, number):
+        super().__init__()
+        self.number = number
+
+    @staticmethod
+    def fibo(n):
+        if n == 0:
+            return 1
+        else:
+            return n * FibonacciThread.fibo(n - 1)
+
+    def run(self):
+        result = self.fibo(self.number)
+        time.sleep(random.randint(5, 20))
+        print(f"{self.number}! = {result}")
+
+
+for number in range(10):
+    FibonacciThread(number).start()