对动态网页进行逆向工程

通过搜索字母表的每个字母，然后遍历json响应的结果页面，来抓取所有国家信息。其产生结果将会存储在表格当中。

import stringfrom downloader import Downloaderimport jsonD = Downloader()template_url = 'http://example.webscraping.com/ajax/search.json?page={}&page_size=10&search_term={}'countries = set()for letter in string.lowercase:    page = 0    while True:        html = D(template_url.format(page, letter))        try:            ajax = json.loads(html)#将json格式的数据解析成一个字典        except ValueError as e:            print e            ajax = None        else:            for record in ajax['records']:                countries.add(record['country'])        page += 1        if ajax is None or page >= ajax['num_pages']:            breakopen('countries.txt', 'w').write('\n'.join(sorted(countries)))