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

# -*-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Connecti 错误，这个情况不做重试
 except requests.exceptions.Connecti  as e:
  return
 return html
 
url_retry(\"http://httpbin.org/status/404\")

# -*-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()

# -*-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\")

# -*-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()