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要提高Python爬虫的抓取速度,可以采取以下几种方法:
threading
和multiprocessing
库实现并发请求。示例代码(多线程):
import threading
import requests
def fetch(url):
response = requests.get(url)
# 处理响应数据
urls = ['http://example.com'] * 10
threads = []
for url in urls:
t = threading.Thread(target=fetch, args=(url,))
t.start()
threads.append(t)
for t in threads:
t.join()
示例代码(多进程):
import multiprocessing
import requests
def fetch(url):
response = requests.get(url)
# 处理响应数据
urls = ['http://example.com'] * 10
processes = []
for url in urls:
p = multiprocessing.Process(target=fetch, args=(url,))
p.start()
processes.append(p)
for p in processes:
p.join()
aiohttp
)实现非阻塞I/O操作,提高抓取速度。示例代码(aiohttp):
import aiohttp
import asyncio
async def fetch(url):
async with aiohttp.ClientSession() as session:
async with session.get(url) as response:
# 处理响应数据
async def main():
urls = ['http://example.com'] * 10
tasks = [fetch(url) for url in urls]
await asyncio.gather(*tasks)
asyncio.run(main())
BeautifulSoup
或lxml
)解析HTML文档,减少解析时间。示例代码(BeautifulSoup):
from bs4 import BeautifulSoup
import requests
def parse(html):
soup = BeautifulSoup(html, 'html.parser')
# 解析数据
response = requests.get('http://example.com')
html = response.text
parse(html)
示例代码(lxml):
from lxml import etree
import requests
def parse(html):
tree = etree.HTML(html)
# 解析数据
response = requests.get('http://example.com')
html = response.text
parse(html)
示例代码(使用免费代理IP):
import requests
proxies = {
'http': 'http://proxy.example.com:8080',
'https': 'http://proxy.example.com:8080',
}
response = requests.get('http://example.com', proxies=proxies)
示例代码(使用time.sleep
):
import time
import requests
url = 'http://example.com'
response = requests.get(url)
# 处理响应数据
time.sleep(1) # 暂停1秒
示例代码(使用pickle
库):
import requests
import pickle
def save_cache(data, file_name):
with open(file_name, 'wb') as f:
pickle.dump(data, f)
def load_cache(file_name):
with open(file_name, 'rb') as f:
return pickle.load(f)
url = 'http://example.com'
file_name = 'cache.pkl'
if os.path.exists(file_name):
data = load_cache(file_name)
else:
response = requests.get(url)
data = parse(response.text)
save_cache(data, file_name)
通过以上方法,可以有效地提高Python爬虫的抓取速度。
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