python出现RuntimeError错误问题及解决

这篇文章主要介绍了python出现RuntimeError错误问题及解决方案，具有很好的参考价值，希望对大家有所帮助。如有错误或未考虑完全的地方，望不吝赐教

下面是出现的错误解释

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.

下面是出现错误代码的原代码

import multiprocessing as mp import time from urllib.request import urlopen,urljoin from bs4 import BeautifulSoup import re base_url = "https://morvanzhou.github.io/" #crawl爬取网页 def crawl(url): response = urlopen(url) time.sleep(0.1) return response.read().decode() #parse解析网页 def parse(html): soup = BeautifulSoup(html,'html.parser') urls = soup.find_all('a',{"href":re.compile('^/.+?/$')}) title = soup.find('h1').get_text().strip() page_urls = set([urljoin(base_url,url['href'])for url in urls]) url = soup.find('meta',{'property':"og:url"})['content'] return title,page_urls,url unseen = set([base_url]) seen = set() restricted_crawl = True pool = mp.Pool(4) count, t1 = 1, time.time() while len(unseen) != 0:                 # still get some url to visit if restricted_crawl and len(seen) > 20: break print('\nDistributed Crawling...') crawl_jobs = [pool.apply_async(crawl, args=(url,)) for url in unseen] htmls = [j.get() for j in crawl_jobs]      # request connection print('\nDistributed Parsing...') parse_jobs = [pool.apply_async(parse, args=(html,)) for html in htmls] results = [j.get() for j in parse_jobs]    # parse html print('\nAnalysing...') seen.update(unseen)         # seen the crawled unseen.clear()              # nothing unseen for title, page_urls, url in results: print(count, title, url) count += 1 unseen.update(page_urls - seen)     # get new url to crawl print('Total time: %.1f s' % (time.time()-t1))    # 16 s !!!

这是修改后的正确代码

import multiprocessing as mp import time from urllib.request import urlopen,urljoin from bs4 import BeautifulSoup import re   base_url = "https://morvanzhou.github.io/"   #crawl爬取网页 def crawl(url):     response = urlopen(url)     time.sleep(0.1)     return response.read().decode()   #parse解析网页 def parse(html):     soup = BeautifulSoup(html,'html.parser')     urls = soup.find_all('a',{"href":re.compile('^/.+?/$')})     title = soup.find('h1').get_text().strip()     page_urls = set([urljoin(base_url,url['href'])for url in urls])     url = soup.find('meta',{'property':"og:url"})['content']     return title,page_urls,url   def main():     unseen = set([base_url])     seen = set()     restricted_crawl = True       pool = mp.Pool(4)     count, t1 = 1, time.time()     while len(unseen) != 0:                 # still get some url to visit         if restricted_crawl and len(seen) > 20:                 break         print('\nDistributed Crawling...')         crawl_jobs = [pool.apply_async(crawl, args=(url,)) for url in unseen]         htmls = [j.get() for j in crawl_jobs]      # request connection           print('\nDistributed Parsing...')         parse_jobs = [pool.apply_async(parse, args=(html,)) for html in htmls]         results = [j.get() for j in parse_jobs]    # parse html           print('\nAnalysing...')         seen.update(unseen)         # seen the crawled         unseen.clear()              # nothing unseen           for title, page_urls, url in results:             print(count, title, url)             count += 1             unseen.update(page_urls - seen)     # get new url to crawl     print('Total time: %.1f s' % (time.time()-t1))    # 16 s !!!     if __name__ == '__main__':     main()

综上可知，就是把你的运行代码整合成一个函数，然后加入