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requests & grequests
requests 和 grequests 是Python中用于发送HTTP请求的不同库。requests 是一个同步、阻塞式库,而 grequests 是基于 requests 封装的异步非阻塞库,它利用了 gevent 库提供的协程机制,能够并发发送多个请求。
选择哪个库取决于你的需求:
当你只需要顺序发送少量请求,或者不关心请求之间并发性能的时候,requests 是一个很好的选择,因为它易于理解和使用。
当你需要并发处理大量HTTP请求,提高整体性能,尤其是网络IO密集型任务时,如爬虫抓取大量页面、API服务端并发请求下游服务等场景下,grequests 更合适。
单线程同步请求(使用requests)
-
import requests -
urls = ["https://example.com/page1", "https://example.com/page2", "https://example.com/page3"] -
# 单线程同步请求 -
responses = [requests.get(url) for url in urls] -
# 处理响应 -
for response in responses: -
print(response.text)
多线程同步请求(使用requests配合threading)
-
import requests -
import threading -
# 创建一个处理请求的函数 -
def fetch_page(url): -
response = requests.get(url) -
return response.text -
urls = ["https://example.com/page1", "https://example.com/page2", "https://example.com/page3"] -
threads = [] -
# 启动多线程请求 -
for url in urls: -
thread = threading.Thread(target=fetch_page, args=(url,)) -
threads.append(thread) -
thread.start() -
# 等待所有线程完成 -
for thread in threads: -
thread.join() -
# 假设你有一个列表存储结果 -
results = [result for result in thread_results]
异步并发请求(使用grequests)
-
import grequests -
urls = ["https://example.com/page1", "https://example.com/page2", "https://example.com/page3"] -
# 异步并发请求 -
rs = (grequests.get(url) for url in urls) -
responses = grequests.map(rs) -
# 处理响应 -
for response in responses: -
print(response.text)
超时控制(grequests可以更方便地处理超时)
-
import grequests -
# 对每个请求设置超时时间为5秒 -
urls = [("https://example.com/page{}".format(i), {'timeout': 5}) for i in range(1, 4)] -
rs = (grequests.get(url, **kwargs) for url, kwargs in urls) -
responses = grequests.map(rs) -
for response in responses: -
if response is not None: -
print(response.text) -
else: -
print(f"Request timed out for {response.request.url}")
带异常处理的异步请求(grequests可以在一个循环中统一处理异常)
-
import grequests -
urls = ["https://example.com/page1", "https://example.com/page2", "https://example.com/page3"] -
rs = [grequests.get(url) for url in urls] -
def handle_exception(request, exception): -
print(f"Error on URL {request.url}: {exception}") -
responses = grequests.map(rs, size=10, exception_handler=handle_exception) -
for response in responses: -
if response is not None: -
print(f"{response.request.url} - Response: {response.text}")
在最后这个例子中,grequests.map() 同时发送多个请求,当有请求发生异常时,通过自定义的 exception_handler 函数来处理异常,而不是让整个程序崩溃。同时,size 参数指定了最大并发数,有助于避免一次性发起过多请求导致服务器压力过大。
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