python爬虫多次请求超时的几种重试方法(6种)

第一种方法

headers = dict()
url = 'https://www.baidu.com'
try:
 proxies = none
 response = requests.get(url, headers=headers, verify=false, proxies=none, timeout=3)
except:
 # logdebug('requests failed one time')
 try:
  proxies = none
  response = requests.get(url, headers=headers, verify=false, proxies=none, timeout=3)
 except:
  # logdebug('requests failed two time')
  print('requests failed two time')

总结：代码比较冗余，重试try的次数越多，代码行数越多，但是打印日志比较方便

第二种方法

def requestdemo(url，):
 headers = dict()
 trytimes = 3 # 重试的次数
 for i in range(trytimes):
 try:
  proxies = none
  response = requests.get(url, headers=headers, verify=false, proxies=none, timeout=3)
  # 注意此处也可能是302等状态码
  if response.status_code == 200:
  break
 except:
  # logdebug(f'requests failed {i}time')
   print(f'requests failed {i} time')

总结：遍历代码明显比第一个简化了很多，打印日志也方便

第三种方法

def requestdemo(url， times=1):
 headers = dict()
 try:
  proxies = none
  response = requests.get(url, headers=headers, verify=false, proxies=none, timeout=3)
  html = response.text()
  # todo 此处处理代码正常逻辑
  pass
  return html
 except:
  # logdebug(f'requests failed {i}time')
  trytimes = 3 # 重试的次数
  if times < trytimes:
  times += 1
   return requestdemo(url， times)
  return 'out of maxtimes'

总结：迭代显得比较高大上，中间处理代码时有其它错误照样可以进行重试；缺点不太好理解，容易出错，另外try包含的内容过多时，对代码运行速度不利。

第四种方法

@retry(3) # 重试的次数 3
def requestdemo(url):
 headers = dict()
 proxies = none
 response = requests.get(url, headers=headers, verify=false, proxies=none, timeout=3)
 html = response.text()
 # todo 此处处理代码正常逻辑
 pass
 return html
 
def retry(times):
 def wrapper(func):
  def inner_wrapper(*args, **kwargs):
   i = 0
   while i < times:
    try:
     print(i)
     return func(*args, **kwargs)
    except:
     # 此处打印日志 func.__name__ 为say函数
     print("logdebug: {}()".format(func.__name__))
     i += 1
  return inner_wrapper
 return wrapper

总结：装饰器优点多种函数复用，使用十分方便

第五种方法

#!/usr/bin/python
# -*-coding='utf-8' -*-
import requests
import time
import json
from lxml import etree
import warnings
warnings.filterwarnings("ignore")

def get_xiaomi():
 try:
  # for n in range(5): # 重试5次
  #  print("第"+str(n)+"次")
  for a in range(5): # 重试5次
   print(a)
   url = "https://www.mi.com/"
   headers = {
    "accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3",
    "accept-encoding": "gzip, deflate, br",
    "accept-language": "zh-cn,zh;q=0.9,en;q=0.8",
    "connection": "keep-alive",
    # "cookie": "xmuuid=xmguest-d80d9ce0-910b-11ea-8ee0-3131e8ff9940; hm_lvt_c3e3e8b3ea48955284516b186acf0f4e=1588929065; xm_agreement=0; pageid=81190ccc4d52f577; lastsource=www.baidu.com; mstuid=1588929065187_5718; log_code=81190ccc4d52f577-e0f893c4337cbe4d|https%3a%2f%2fwww.mi.com%2f; hm_lpvt_c3e3e8b3ea48955284516b186acf0f4e=1588929099; mstz=||1156285732.7|||; xm_vistor=1588929065187_5718_1588929065187-1588929100964",
    "host": "www.mi.com",
    "upgrade-insecure-requests": "1",
    "user-agent": "mozilla/5.0 (windows nt 10.0; win64; x64) applewebkit/537.36 (khtml, like gecko) chrome/75.0.3770.90 safari/537.36"
   }
   response = requests.get(url,headers=headers,timeout=10,verify=false)
   html = etree.html(response.text)
   # print(html)
   result = etree.tostring(html)
   # print(result)
   print(result.decode("utf-8"))
   title = html.xpath('//head/title/text()')[0]
   print("title==",title)
   if "左左" in title:
   # print(response.status_code)
   # if response.status_code ==200:
    break
  return title

 except:
  result = "异常"
  return result

if __name__ == '__main__':
 print(get_xiaomi())

第六种方法

python重试模块retrying

# 设置最大重试次数
@retry(stop_max_attempt_number=5)
def get_proxies(self):
 r = requests.get('代理地址')
 print('正在获取')
 raise exception("异常")
 print('获取到最新代理 = %s' % r.text)
 params = dict()
 if r and r.status_code == 200:
  proxy = str(r.content, encoding='utf-8')
  params['http'] = 'http://' + proxy
  params['https'] = 'https://' + proxy

# 设置方法的最大延迟时间，默认为100毫秒(是执行这个方法重试的总时间)
@retry(stop_max_attempt_number=5,stop_max_delay=50)
# 通过设置为50，我们会发现，任务并没有执行5次才结束！

# 添加每次方法执行之间的等待时间
@retry(stop_max_attempt_number=5,wait_fixed=2000)
# 随机的等待时间
@retry(stop_max_attempt_number=5,wait_random_min=100,wait_random_max=2000)
# 每调用一次增加固定时长
@retry(stop_max_attempt_number=5,wait_incrementing_increment=1000)

# 根据异常重试，先看个简单的例子
def retry_if_io_error(exception):
 return isinstance(exception, ioerror)

@retry(retry_on_exception=retry_if_io_error)
def read_a_file():
 with open("file", "r") as f:
  return f.read()

read_a_file函数如果抛出了异常，会去retry_on_exception指向的函数去判断返回的是true还是false，如果是true则运行指定的重试次数后，抛出异常，false的话直接抛出异常。

当时自己测试的时候网上一大堆抄来抄去的，意思是retry_on_exception指定一个函数，函数返回指定异常，会重试，不是异常会退出。真坑人啊！

来看看获取代理的应用(仅仅是为了测试retrying模块)

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