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()

来源：https://blog.csdn.net/u013055678/article/details/54290481