chap 16: error occurred while running multiprocess crawling code

[pejapie]

from urllib.request import urlopen
from bs4 import BeautifulSoup
import re
import random

from multiprocessing import Process
import os
import time

visited = []
def get_links(bs):
    print('Getting links in {}'.format(os.getpid()))
    links = bs.find('div', {'id':'bodyContent'}).find_all('a', href=re.compile('^(/wiki/)((?!:).)*$'))
    return [link for link in links if link not in visited]

def scrape_article(path):
    visited.append(path)
    html = urlopen('http://en.wikipedia.org{}'.format(path))
    time.sleep(3)
    bs = BeautifulSoup(html, 'html.parser')
    title = bs.find('h1').get_text()
    print('Scraping {} in process {}'.format(title, os.getpid()))
    links = get_links(bs)
    if len(links) > 0:
        newArticle = links[random.randint(0, len(links)-1)].attrs['href']
        print(newArticle)
        scrape_article(newArticle)

processes = []
processes.append(Process(target=scrape_article, args=('/wiki/Kevin_Bacon', )))
processes.append(Process(target=scrape_article, args=('/wiki/Monty_Python', )))

for p in processes:
    p.start()

following error occurred while running it

RuntimeError: 
        An attempt has been made to start a new process before the
        current process has finished its bootstrapping phase.

        This probably means that you are not using fork to start your
        child processes and you have forgotten to use the proper idiom
        in the main module:

            if __name__ == '__main__':
                freeze_support()
                ...

        The "freeze_support()" line can be omitted if the program
        is not going to be frozen to produce an executable.

changed code to this:

# inserted if__name__=='__main__':
if __name__ == '__main__':
    processes = []
    processes.append(Process(target=scrape_article, args=('/wiki/Kevin_Bacon', )))
    processes.append(Process(target=scrape_article, args=('/wiki/Monty_Python', )))
    
    for p in processes:
        p.start()