需求：抓取网站https://www.edge.org/library所有的书名、作者以及作者的维基百科简介
工具：PyCharm
第三方库：requests、BeautifulSoup
import requests
from bs4 import BeautifulSoup
爬虫有两种方式，一种是模拟请求获取返回数据即可，另一种需要解析HTML。本次爬虫方式就是后者。
BeautifulSoup是解析HTML的库。
初次写爬虫，一开始傻不拉几的用同步方式，依次获取所有的页面的数据，总共耗时2个多小时，令人发指。后来自己摸索，分别采用多进程/多线程/多协程的方式，效率惊人。
说到进程池，Python提供了两种创建方式，直接上代码：
import re
import time
from concurrent.futures import ThreadPoolExecutor, ProcessPoolExecutor
from multiprocessing.pool import Pool
import requests
import sys
from bs4 import BeautifulSoup
from book.ExcelUtils import ExcelUtils
headers = {
'user-agent': 'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.99 Safari/537.36'}
# 获取书名、作者、作者wiki简介
def get_book_info(url):
book_dict = {'name': [], 'author': [], 'info': []}
res = requests.get(url, headers=headers)
if res.status_code == 200:
find_book_name_list = re.findall('<div class="views-field views-field-title">.*?<a href=.*?>(.*?)</a>',
res.text)
book_dict['name'] = find_book_name_list
find_author_list = re.findall(
'<span class="views-field views-field-field-edge-author">.*?<a href=".*?">(.*?)</a>', res.text)
book_dict['author'] = find_author_list
# 获取作者wiki简介
get_wiki_author_info(find_author_list, book_dict)
else:
print('get_book_info is failed, url:[%s]' % url)
return book_dict
# 根据作者名字获取作者wiki简介
def get_wiki_author_info(find_author_list, book_dict):
for name in find_author_list:
url = 'https://en.wikipedia.org/wiki/%s' % name.replace(' ', '_')
try:
res = requests.get(url, headers=headers)
if res.status_code == 200:
soup = BeautifulSoup(res.text, "html.parser")
soup_select = soup.select('#mw-content-text p')
if str.strip(soup_select[0].get_text()) != '':
if soup_select[0].get_text().find('may refer to') != -1:
# 存在多种选项
name_list = soup.select('#mw-content-text li a')
for index, item in enumerate(name_list):
if item.get_text().find(name) != -1:
# 递归，默认只取第一个匹配的
get_wiki_author_info([item.get_text()], book_dict)
break
else:
book_dict['info'].append(soup_select[0].get_text())
else:
book_dict['info'].append(soup_select[1].get_text())
else:
book_dict['info'].append('get failed, url:[%s]' % url)
print('get_wiki_author_info is failed, url:[%s]' % url)
except:
book_dict['info'].append('get exception, url:[%s]' % url)
# 进程池的一种创建方式
def pool_test(url_list):
book_list = []
# 创建进程池
pool = Pool(20)
start = time.time()
for url in url_list:
time.sleep(0.5)
result = pool.apply_async(get_book_info, args=(url,))
book_list.append(result)
# 关闭进程池，不再接受新的进程，依旧处理未处理完的任务
pool.close()
# 主进程等待所有子进程执行完毕，必须在close或terminate之后
pool.join()
print('time: ', time.time() - start)
book_name_list = []
author_list = []
author_info_list = []
print('book_list: ', len(book_list))
for v in book_list:
book_name_list.extend(v.get()['name'])
author_list.extend(v.get()['author'])
author_info_list.extend(v.get()['info'])
ExcelUtils.write_data_to_excel('bookInfo', book_name_list, author_list, author_info_list)
# 线程池的创建方式
def thread_pool_test(url_list):
book_list = []
# 创建线程池
pool = ThreadPoolExecutor(max_workers=20)
start = time.time()
for url in url_list:
time.sleep(0.5)
result = pool.submit(get_book_info, url)
book_list.append(result)
pool.shutdown()
print('time: ', time.time() - start)
book_name_list = []
author_list = []
author_info_list = []
print('book_list: ', len(book_list))
for future in book_list:
book_name_list.extend(future.result()['name'])
author_list.extend(future.result()['author'])
author_info_list.extend(future.result()['info'])
ExcelUtils.write_data_to_excel('bookInfo', book_name_list, author_list, author_info_list)
# 进程池的另外一种创建方式，跟线程池的创建方式一样。其方法等也相同。
def process_pool_test(url_list):
book_list = []
# 创建进程池
pool = ProcessPoolExecutor(max_workers=20)
start = time.time()
for url in url_list:
time.sleep(0.5)
result = pool.submit(get_book_info, url)
book_list.append(result)
pool.shutdown()
print('time: ', time.time() - start)
book_name_list = []
author_list = []
author_info_list = []
print('book_list: ', len(book_list))
for future in book_list:
book_name_list.extend(future.result()['name'])
author_list.extend(future.result()['author'])
author_info_list.extend(future.result()['info'])
ExcelUtils.write_data_to_excel('bookInfo', book_name_list, author_list, author_info_list)
if __name__ == '__main__':
sys.setrecursionlimit(10000)
url_list = ['https://www.edge.org/library']
for i in range(1, 52):
url_list.append('https://www.edge.org/library?page=%s' % i)
thread_pool_test(url_list)
Python协程爬虫，代码相对于进程线程，稍微麻烦了一点，如下：
import asyncio
import aiohttp
import re
import time
import sys
from bs4 import BeautifulSoup
from spider.ExcelUtils import ExcelUtils
headers = {
'user-agent': 'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.99 Safari/537.36'}
# 获取书名、作者
async def get_book_info(url, semaphore):
book_dict = {'name': [], 'author': []}
async with semaphore:
async with aiohttp.ClientSession() as session:
async with session.get(url, headers=headers) as res:
if res.status == 200:
text = await res.text()
find_book_name_list = re.findall(
'<div class="views-field views-field-title">.*?<a href=.*?>(.*?)</a>', text)
book_dict['name'] = find_book_name_list
find_author_list = re.findall(
'<span class="views-field views-field-field-edge-author">.*?<a href=".*?">(.*?)</a>', text)
book_dict['author'] = find_author_list
else:
print('get_book_info is failed, url:[%s]' % url)
return book_dict
# 根据作者名字获取作者wiki简介
async def get_wiki_author_info(name, semaphore):
url = 'https://en.wikipedia.org/wiki/%s' % name.replace(' ', '_')
try:
async with semaphore:
async with aiohttp.ClientSession() as session:
async with session.get(url, headers=headers) as res:
if res.status == 200:
text = await res.text()
soup = BeautifulSoup(text, "html.parser")
soup_select = soup.select('#mw-content-text p')
if str.strip(soup_select[0].get_text()) != '':
if soup_select[0].get_text().find('may refer to') != -1:
# 存在多种选项
name_list = soup.select('#mw-content-text li a')
for index, item in enumerate(name_list):
if item.get_text().find(name) != -1:
# 递归，默认只取第一个匹配的
await get_wiki_author_info([item.get_text(), semaphore])
break
else:
return soup_select[0].get_text()
else:
return soup_select[1].get_text()
else:
print('get_wiki_author_info is failed, url:[%s]' % url)
return 'get failed, url:[%s]' % url
except:
return 'get exception, url:[%s]' % url
if __name__ == '__main__':
sys.setrecursionlimit(10000)
url_list = ['https://www.edge.org/library']
for i in range(1, 52):
url_list.append('https://www.edge.org/library?page=%s' % i)
# 信号量，限制并发数，类比20个线程
semaphore = asyncio.Semaphore(20)
loop = asyncio.get_event_loop()
tasks = [asyncio.ensure_future(get_book_info(url, semaphore)) for url in url_list]
start = time.time()
loop.run_until_complete(asyncio.wait(tasks))
book_name_list = []
author_list = []
print('book_list: ', len(tasks))
for future in tasks:
book_name_list.extend(future.result()['name'])
author_list.extend(future.result()['author'])
# 获取作者wiki简介
wiki_tasks = [asyncio.ensure_future(get_wiki_author_info(name, semaphore)) for name in author_list]
loop.run_until_complete(asyncio.wait(wiki_tasks))
author_info_list = [future.result() for future in wiki_tasks]
print('time: ', time.time() - start)
ExcelUtils.write_data_to_excel('bookInfo', book_name_list, author_list, author_info_list)
ExcelUtils工具类的代码如下：
import xlwt
class ExcelUtils:
@staticmethod
def def_style():
style = xlwt.XFStyle()
alignment = xlwt.Alignment()
alignment.horz = xlwt.Alignment.HORZ_CENTER # 水平居中
alignment.vert = xlwt.Alignment.VERT_CENTER # 垂直居中
style.alignment = alignment
return style
@staticmethod
def write_data_to_excel(excel_name, book_name_list, author_list, author_info_list):
# 实例化一个Workbook()对象(即excel文件)
wbk = xlwt.Workbook()
# 新建一个名为Sheet1的excel sheet。此处的cell_overwrite_ok =True是为了能对同一个单元格重复操作。
sheet = wbk.add_sheet('Sheet1', cell_overwrite_ok=True)
col_1 = sheet.col(0)
col_2 = sheet.col(1)
col_3 = sheet.col(2)
col_1.width = 256 * 45
col_2.width = 256 * 30
col_3.width = 256 * 200
sheet.write(0, 0, '书名', ExcelUtils.def_style())
sheet.write(0, 1, '作者', ExcelUtils.def_style())
sheet.write(0, 2, '作者简介', ExcelUtils.def_style())
for i in range(len(author_info_list)):
sheet.write(i + 1, 0, book_name_list[i])
sheet.write(i + 1, 1, author_list[i], ExcelUtils.def_style())
sheet.write(i + 1, 2, author_info_list[i])
wbk.save(excel_name + '.xls')
四种方式每次的实验时间都不同，这里只取其中一次的执行时间，如下：
多进程 Pool(20)
time: 215.41232109069824秒
数据总数：1421
多进程 ProcessPoolExecutor(max_workers=20)
time: 202.88900017738342秒
数据总数：1481
多线程：ThreadPoolExecutor(max_workers=20)
time: 198.67899990081787秒
数据总数：1481
协程： async
time: 166.4319999217987秒
数据总数：1481
可以看出这四者的效率差别并不大，由于每次时间都不同，也不能确切的说哪种方式更优。
不过根据前面讲的进程、线程、协程，一般情况下。协程执行效率是高于线程的，Pool的效率高于ProcessPoolExecutor。但是协程是单线程的，无法利用多核CPU，组合应用的时候，推荐Pool + 协程。
