add concurrence examples

Concurrence_examples/README.md

@@ -1,3 +1,3 @@
 ### Concurrence in Python
 
-* This directory contains the examples for my Medium article: [Python + Concurrence: Here is What You Need to Know](https://medium.com/python-for-the-utopian/python-concurrence-here-is-what-you-need-to-know-c771d86eda95).
+Examples for my Medium article: [Python + Concurrence: A Mnemonic Guide🚦](https://medium.com/python-for-the-utopian/python-concurrence-a-mnemonic-guide-7304867cbfb7).

Concurrence_examples/asyncio_simple_example.py

@@ -2,14 +2,13 @@
 
 import asyncio
 
+
 async def delayed_hello():
-    print("Hello ")
+    print('Hello ')
     await asyncio.sleep(1)
-    print("World!")
+    print('World!')
 
 
-if __name__ == "__main__":
-    
-    loop = asyncio.get_event_loop()
-    loop.run_until_complete(delayed_hello())
-    loop.close()
+loop = asyncio.get_event_loop()
+loop.run_until_complete(delayed_hello())
+loop.close()

Concurrence_examples/concurrence_future_example.py

@@ -1,25 +0,0 @@
-#!/usr/bin/env python3
-
-import random
-import logging
-import concurrent.futures
-
-WORKER_COUNT = 10
-JOB_COUNT = 10
-
-class Job:
-    def __init__(self, number):
-        self.number = number
-
-def process_job(job):
-    # Wait between 0 and 0.01 seconds.
-    time.sleep(random.random()/100.0)
-    logging.info("Job number {:d}".format(job.number))
-    
-def main():
-    with concurrent.futures.ThreadPoolExecutor(
-         max_workers=WORKER_COUNT) as executor:
-       futures = [executor.submit(process_job, Job(i))
-                        for i in range(JOB_COUNT)]
-       for future in concurrent.futures.as_completed(futures):
-           pass

Concurrence_examples/concurrent_future_example.py

@@ -0,0 +1,19 @@
+#!/usr/bin/env python3
+
+from time import sleep
+from concurrent.futures import ThreadPoolExecutor
+
+
+def return_after_5_secs(message):
+    sleep(5)
+    return message
+
+
+pool = ThreadPoolExecutor(3)
+future = pool.submit(return_after_5_secs, ('Future message'))
+
+print(future.done())
+
+sleep(5)
+print(future.done())
+print(future.result())

Concurrence_examples/concurrent_tasks.py

@@ -1,51 +0,0 @@
-#!/usr/bin/env python3
-
-import os
-import time
-import threading
-import multiprocessing
- 
-NUM_WORKERS = 4
- 
-def run_sleep():
-    print("PID: %s, Process Name: %s, Thread Name: %s" % (
-        os.getpid(),
-        multiprocessing.current_process().name,
-        threading.current_thread().name)
-    )
-    time.sleep(1)
- 
- 
-# Run tasks serially
-start_time = time.time()
-
-for _ in range(NUM_WORKERS):
-    run_sleep()
-
-end_time = time.time()
- 
-print("Serial time=", end_time - start_time)
- 
-
-# Run tasks using threads
-start_time = time.time()
-
-threads = [threading.Thread(target=run_sleep) for _ in range(NUM_WORKERS)]
-[thread.start() for thread in threads]
-[thread.join() for thread in threads]
-
-end_time = time.time()
- 
-print("Threads time=", end_time - start_time)
- 
-
-# Run tasks using processes
-start_time = time.time()
-
-processes = [multiprocessing.Process(target=run_sleep()) for _ in range(NUM_WORKERS)]
-[process.start() for process in processes]
-[process.join() for process in processes]
-
-end_time = time.time()
- 
-print("Parallel time=", end_time - start_time)

Concurrence_examples/concurrent_tasks_with_math.py

@@ -1,49 +0,0 @@
-#!/usr/bin/env python3
-
-import os
-import time
-import threading
-import multiprocessing
-
-NUM_WORKERS = 4
-
-def run_numbers():
-    print("PID: %s, Process Name: %s, Thread Name: %s" % (
-        os.getpid(),
-        multiprocessing.current_process().name,
-        threading.current_thread().name)
-    )
-    x = 0
-    while x < 10000000:
-        x += 1
-
-start_time = time.time()
-
-for _ in range(NUM_WORKERS):
-    run_numbers()
-
-end_time = time.time()
- 
-print("Serial time=", end_time - start_time)
- 
-
-start_time = time.time()
-
-threads = [threading.Thread(target=run_numbers) for _ in range(NUM_WORKERS)]
-[thread.start() for thread in threads]
-[thread.join() for thread in threads]
-
-end_time = time.time()
- 
-print("Threads time=", end_time - start_time)
- 
- 
-start_time = time.time()
-
-processes = [multiprocessing.Process(target=run_numbers) for _ in range(NUM_WORKERS)]
-[process.start() for process in processes]
-[process.join() for process in processes]
-end_time = time.time()
-
- 
-print("Parallel time=", end_time - start_time)

Concurrence_examples/daemon_example.py

@@ -7,10 +7,10 @@ import multiprocessing
 
 def daemon():
     p = multiprocessing.current_process()
-
     print('Starting: {}, {}'.format(p.name, p.pid))
+
     sys.stdout.flush()
-    time.sleep(2)
+    time.sleep(1)
     print('Exiting : {}, {}'.format(p.name, p.pid))
 
     sys.stdout.flush()
@@ -18,8 +18,8 @@ def daemon():
 
 def non_daemon():
     p = multiprocessing.current_process()
-
     print('Starting: {}, {}'.format(p.name, p.pid))
+
     sys.stdout.flush()
     print('Exiting : {}, {}'.format(p.name, p.pid))
 

Concurrence_examples/deadlock_example.py

@@ -0,0 +1,12 @@
+#!/usr/bin/env python3
+
+import threading 
+
+l = threading.Lock()
+print("Before first lock acquire.")
+
+l.acquire()
+print("Before second lock acquire.")
+
+l.acquire()
+print("Lock was acquired twice")

Concurrence_examples/getenv_example.py

@@ -1,24 +0,0 @@
-#!/usr/bin/env python3
-
-import time
-from gevent.pool import Pool
-from gevent import monkey
- 
-# Note that you can spawn many workers with gevent since the cost of creating and switching is very low
-NUM_WORKERS = 4
- 
-# Monkey-Patch socket module for HTTP requests
-monkey.patch_socket()
- 
-start_time = time.time()
- 
-pool = Pool(NUM_WORKERS)
-for address in WEBSITE_LIST:
-    pool.spawn(check_website, address)
- 
-# Wait for stuff to finish
-pool.join()
-         
-end_time = time.time()        
- 
-print("Time for GreenSquirrel: %ssecs" % (end_time - start_time))

Concurrence_examples/logging_example.py

@@ -1,15 +1,16 @@
 #!/usr/bin/env python3
 
-import multiprocessing
-import logging
 import sys
+import logging
+import multiprocessing
+
 
 def worker():
-    print 'Doing some work'
+    print('Doing some work...')
     sys.stdout.flush()
 
-if __name__ == '__main__':
-    multiprocessing.log_to_stderr(logging.DEBUG)
-    p = multiprocessing.Process(target=worker)
-    p.start()
-    p.join()
+
+multiprocessing.log_to_stderr(logging.DEBUG)
+p = multiprocessing.Process(target=worker)
+p.start()
+p.join()

Concurrence_examples/multiprocessing_example.py

@@ -1,5 +1,3 @@
-#!/usr/bin/env python3
-
 import time
 import random
 import multiprocessing
@@ -12,5 +10,5 @@ def worker(n):
 
 
 for i in range(5):
-    t = multiprocessing.Process(target=worker, args=(i,))
-    t.start()
+    p = multiprocessing.Process(target=worker, args=(i,))
+    p.start()

Concurrence_examples/pool_example.py

@@ -2,9 +2,10 @@
 
 from multiprocessing import Pool
 
+
 def f(x):
     return x*x
 
-if __name__ == '__main__':
-    p = Pool(5)
-    print(p.map(f, [1, 2, 3]))
+
+p = Pool(5)
+print(p.map(f, [1, 2, 3]))

Concurrence_examples/safe_thread_example.py

@@ -1,26 +0,0 @@
-#!/usr/bin/env python3
-
-import threading
-
-counter = 0
-threads = []
-
-lock = threading.Lock()
-
-
-def count_with_lock():
-
-    global counter
-
-    for _ in range(100):
-        with lock:
-            counter += 1
-
-
-for _ in range(100):
-    thread = threading.Thread(target=count_with_lock)
-    thread.start()
-    threads.append(thread)
-
-
-print(counter)

Concurrence_examples/threads_with_queues.py

@@ -1,36 +1,19 @@
-#!/usr/bin/env python3
-
-import time
 from queue import Queue
 from threading import Thread
- 
+
+
 NUM_WORKERS = 4
 task_queue = Queue()
- 
+
+
 def worker():
-    # Constantly check the queue for addresses
     while True:
         address = task_queue.get()
         run_function(address)
-         
-        # Mark the processed task as done
         task_queue.task_done()
- 
-start_time = time.time()
-         
-# Create the worker threads
+
+
 threads = [Thread(target=worker) for _ in range(NUM_WORKERS)]
- 
-# Add the websites to the task queue
-[task_queue.put(item) for item in SOME_LIST]
- 
-# Start all the workers
+[task_queue.put(item) for item in threads]
 [thread.start() for thread in threads]
- 
-# Wait for all the tasks in the queue to be processed
-task_queue.join()
- 
-         
-end_time = time.time()        
- 
-print('Time: {} secs'.format(end_time - start_time))
+task_queue.join()

Concurrence_examples/unsafe_thread_example.py

@@ -1,22 +0,0 @@
-#!/usr/bin/env python3
-
-import time
-import threading
-
-counter = 0
-threads = []
-
-def count():
-    global counter
-    for _ in range(100):
-        counter += 1
-
-for _ in range(100):
-    thread = threading.Thread(target=count)
-    thread.start()
-    threads.append(thread)
- 
-for thread in threads:
-    thread.join()
-
-print(f"Count: {counter}")