Python Concurrency and Parallelism

multiprocess.py

"""
This tiny test is the difference between concurrence and parallelism in Python.
With the multiprocessing module we have real access to parallelism always that we have more than one CPU core 
"""

import os
from random import randint
from multiprocessing import Process
import time

articles = ["shoes", "t-shirts", "toys"] #simple in-memory database

def add_article(article: str):
    """adds new articles to the existant articles list

    Args:
        article (str): any string you want to add counts as new article
    """
    articles.append(article)

def read_articles(args):
    """Print articles list

    Args:
        args (tuple): packed articles list and index for showing when printing
    """
    articles, index = args
    print("System process PID: {}".format(os.getpid())) # note that this time the PID is every for every thread, this means that every thread is a new process, just if we have several CPU cores
    print("articles list #{}: {}".format(index, articles))
    time_sleep = randint(1, 3)
    time.sleep(time_sleep)
    
def create_thread(articles, index) -> Process:
    """Creates the needed thread

    Args:
        articles (list): needed list for showing with the read_article function
        index (int): needed for printing the list number

    Returns:
        Process: run_thread function needs a process for running it, this is that process
    """
    reader = Process(target=read_articles, args=[(articles, index)])
    return reader
    
def run_thread(thread: Process):
    """Runs the process that we return from create_thread

    Args:
        thread (Process): process returned from create_thread function
    """
    thread.start()
    thread.join()

def show_menu() -> str:
    """ Prints a menu for asking the user if wants to add new elements and return that answer

    Returns:
        str: answer typed
    """
    valid_answer = ["y", "n"]
    answer = input("do you want to add articles to the current list? (y/n)")
    
    if answer in valid_answer:
        return answer
    return "This answer is not valid"

  
if __name__ == '__main__':

    while True:
        
        answer = show_menu()
        
        match (answer): # we do a match and according to the answer some things could happen
            case ("y"):
                article = input("add article: ")
                articles.append(article)
            case ("n"): #if the user does not want to add new articles, we break this loop
                break
            case _:
                print("not a valid option")
            
                
    for i in range(0, 10): # we run a loop with 10 iterations just because we can :)
        thread = create_thread(articles, i) # we send the list and the index, so we can print it in every process
        run_thread(thread)
        time.sleep(1)