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python爬蟲(chóng)URL重試機(jī)制的實(shí)現(xiàn)方法(python2.7以及python3.5)

更新時(shí)間：2018年12月18日 15:13:08 作者：ZJL-阿友

今天小編就為大家分享一篇python爬蟲(chóng)URL重試機(jī)制的實(shí)現(xiàn)方法(python2.7以及python3.5)，具有很好的參考價(jià)值，希望對(duì)大家有所幫助。一起跟隨小編過(guò)來(lái)看看吧

應(yīng)用場(chǎng)景：

狀態(tài)不是200的URL重試多次

代碼比較簡(jiǎn)單還有部分注釋

python2.7實(shí)現(xiàn)：

# -*-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會(huì)拋出HTTPError錯(cuò)誤
  request.raise_for_status()
  html = request.content
 except requests.HTTPError as e:
  html=None
  if num_retries>0:
   #如果不是200就重試，每次遞減重試次數(shù)
   return url_retry(url,num_retries-1)
 #如果url不存在會(huì)拋出ConnectionError錯(cuò)誤，這個(gè)情況不做重試
 except requests.exceptions.ConnectionError as e:
  return
 return html
 
url_retry("http://httpbin.org/status/404")

python3.5實(shí)現(xiàn)：

# -*-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會(huì)拋出HttpProcessingError錯(cuò)誤
    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就重試，每次遞減重試次數(shù)
    return await print_page(url, num_retries - 1)
  #不存在URL會(huì)拋出ClientResponseError錯(cuò)誤
  except aiohttp.errors.ClientResponseError as e:
   return e
 session.close()
 print(body)
 return body
 
def main():
 #這是一個(gè)不存在URL
 # url = 'http://httpbin.org/status/404111'
 #這是一個(gè)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()

爬蟲(chóng)URL重試機(jī)制封裝成修飾器(python2.7以及python3.5以上)

python2.7版本：

# -*-coding:utf-8-*-
"""
ayou
"""
import requests
 
#定義一個(gè)重試修飾器，默認(rèn)重試一次
def retry(num_retries=1):
 #用來(lái)接收函數(shù)
 def wrapper(func):
  #用來(lái)接收函數(shù)的參數(shù)
  def wrapper(*args,**kwargs):
   #為了方便看拋出什么錯(cuò)誤定義一個(gè)錯(cuò)誤變量
   last_exception =None
   #循環(huán)執(zhí)行包裝的函數(shù)
   for _ in range(num_retries):
    try:
     #如果沒(méi)有錯(cuò)誤就返回包裝的函數(shù)，這樣跳出循環(huán)
     return func(*args, **kwargs)
    except Exception as e:
     #捕捉到錯(cuò)誤不要return，不然就不會(huì)循環(huán)了
     last_exception = e
   #如果要看拋出錯(cuò)誤就可以拋出
   # 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
 
#定義一個(gè)重試修飾器，默認(rèn)重試一次
def retry(num_retries=1):
 #用來(lái)接收函數(shù)
 def wrapper(func):
  #用來(lái)接收函數(shù)的參數(shù)
  def wrapper(*args,**kwargs):
   #為了方便看拋出什么錯(cuò)誤定義一個(gè)錯(cuò)誤變量
   last_exception =None
   #循環(huán)執(zhí)行包裝的函數(shù)
   for _ in range(num_retries):
    try:
     #如果沒(méi)有錯(cuò)誤就返回包裝的函數(shù)，這樣跳出循環(huán)
     return func(*args, **kwargs)
    except Exception as e:
     #捕捉到錯(cuò)誤不要return，不然就不會(huì)循環(huán)了
     last_exception = e
   #如果要看拋出錯(cuò)誤就可以拋出
   # 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會(huì)拋出HttpProcessingError錯(cuò)誤
   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()

以上這篇python爬蟲(chóng)URL重試機(jī)制的實(shí)現(xiàn)方法(python2.7以及python3.5)就是小編分享給大家的全部?jī)?nèi)容了，希望能給大家一個(gè)參考，也希望大家多多支持腳本之家。

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