python爬虫URL重试机制的实现方法(python2.7以及python3.5)

应用场景：

状态不是200的URL重试多次

代码比较简单还有部分注释

python2.7实现：

# -*-coding:utf-8-*-
"""
ayou
"""

import requests

def url_retry(url,num_retries=3):
 print("access!")
 try:
  request = requests.get(url,timeout=60)
  #raise_for_status(),如果不是200会抛出HTTPError错误
  request.raise_for_status()
  html = request.content
 except requests.HTTPError as e:
  html=None
  if num_retries>0:
   #如果不是200就重试，每次递减重试次数
   return url_retry(url,num_retries-1)
 #如果url不存在会抛出ConnectionError错误，这个情况不做重试
 except requests.exceptions.ConnectionError as e:
  return
 return html

url_retry("http://httpbin.org/status/404")

python3.5实现：

# -*-coding:utf-8-*-
"""
ayou
"""
import asyncio
import aiohttp

async def print_page(url,num_retries=3):
 async with aiohttp.ClientSession() as session:
  try:
   async with session.get(url,timeout=60) as response:
    print("access!")
     #raise_for_status(),如果不是200会抛出HttpProcessingError错误
    response.raise_for_status()
    body = await response.text()
  except aiohttp.errors.HttpProcessingError as e:
   body = None
   if num_retries > 0:
     #如果不是200就重试，每次递减重试次数
    return await print_page(url, num_retries - 1)
  #不存在URL会抛出ClientResponseError错误
  except aiohttp.errors.ClientResponseError as e:
   return e
 session.close()
 print(body)
 return body

def main():
 #这是一个不存在URL
 # url = 'http://httpbin.org/status/404111'
 #这是一个404的URL
 url = 'http://httpbin.org/status/404'
 loop = asyncio.get_event_loop()
 loop.run_until_complete(print_page(url))
 loop.close()

if __name__ == '__main__':
 main()

爬虫URL重试机制封装成修饰器(python2.7以及python3.5以上)

python2.7版本：

# -*-coding:utf-8-*-
"""
ayou
"""
import requests

#定义一个重试修饰器，默认重试一次
def retry(num_retries=1):
 #用来接收函数
 def wrapper(func):
  #用来接收函数的参数
  def wrapper(*args,**kwargs):
   #为了方便看抛出什么错误定义一个错误变量
   last_exception =None
   #循环执行包装的函数
   for _ in range(num_retries):
    try:
     #如果没有错误就返回包装的函数，这样跳出循环
     return func(*args, **kwargs)
    except Exception as e:
     #捕捉到错误不要return，不然就不会循环了
     last_exception = e
   #如果要看抛出错误就可以抛出
   # raise last_exception
  return wrapper
 return wrapper

if __name__=="__main__":
 @retry(5)
 def url_retry(url):
  request = requests.get(url, timeout=60)
  print("access!")
  request.raise_for_status()
  html = request.content
  print(html)
  return html

 url_retry("http://httpbin.org/status/404")
 # url_retry("http://httpbin.org/status/404111")
 # url_retry("http://www.baidu.com")

python3.5以上版本：

# -*-coding:utf-8-*-
"""
ayou
"""
import aiohttp,asyncio

#定义一个重试修饰器，默认重试一次
def retry(num_retries=1):
 #用来接收函数
 def wrapper(func):
  #用来接收函数的参数
  def wrapper(*args,**kwargs):
   #为了方便看抛出什么错误定义一个错误变量
   last_exception =None
   #循环执行包装的函数
   for _ in range(num_retries):
    try:
     #如果没有错误就返回包装的函数，这样跳出循环
     return func(*args, **kwargs)
    except Exception as e:
     #捕捉到错误不要return，不然就不会循环了
     last_exception = e
   #如果要看抛出错误就可以抛出
   # raise last_exception
  return wrapper
 return wrapper

async def print_page(url):
 async with aiohttp.ClientSession() as session:
  async with session.get(url,timeout=60) as response:
   print("access!")
    #raise_for_status(),如果不是200会抛出HttpProcessingError错误
   response.raise_for_status()
   body = await response.text()
 session.close()
 print(body)
 return body

@retry(5)
def loop_get():
 # url = "http://www.baidu.com"
 # url = 'http://httpbin.org/status/404111'
 url = 'http://httpbin.org/status/404'
 loop = asyncio.get_event_loop()
 loop.run_until_complete(print_page(url))
 loop.close()

if __name__ == '__main__':
 loop_get()

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