Python 爬虫，requests模块，retrying模块

demo.py（retrying模块，多次重新尝试）：

# coding=utf-8
import requests   # 需要pip安装requests模块
from retrying import retry  # 需要pip安装retrying模块


headers={"User-Agent":"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.84 Safari/537.36"}

# @retry 如果出现异常，会多次尝试。
@retry(stop_max_attempt_number=3)  # 最多尝试3次
def _parse_url(url):
    print("*"*20)
    response = requests.get(url, headers=headers, timeout=3)
    assert  response.status_code == 200
    return response.content.decode()


def parse_url(url):
    try:
        html_str = _parse_url(url)
    except:
        html_str = None
    return html_str


if __name__ == '__main__':
    url = "www.baidu.com"   # http://www.baidu.com
    print(parse_url(url))