设置User-Agent，防止反爬虫

def get_one_page(url):
    headers = {
    'User-Agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.116 Safari/537.36'
}
    response = requests.get(url, headers=headers)
    if response.status_code == 200:
        return response.text
    return None