用python写网络爬虫 -从零开始 3 编写ID遍历爬虫

我们在访问网站的时候，发现有些网页ID 是按顺序排列的数字，这个时候我们就可以使用ID遍历的方式来爬取内容。但是局限性在于有些ID数字在10位数左右，那么这样爬取效率就会很低很低！



import itertools
from common import download


def iteration():
    max_errors = 5 # maximum number of consecutive download errors allowed
    num_errors = 0 # current number of consecutive download errors
    for page in itertools.count(1):
        url = ‘http://example.webscraping.com/view/-{}‘.format(page)
        html = download(url)
        if html is None:
            # received an error trying to download this webpage
            num_errors += 1
            if num_errors == max_errors:
                # reached maximum amount of errors in a row so exit
                break
            # so assume have reached the last country ID and can stop downloading
        else:
            # success - can scrape the result
            # ...
            num_errors = 0

用python写网络爬虫 -从零开始 3 编写ID遍历爬虫

原文：http://www.cnblogs.com/mrruning/p/7638459.html