Python: 爬取百度贴吧图片

练习之代码片段，以做备忘：

# encoding=utf8

from __future__ import unicode_literals
import urllib, urllib2
import re
import os
import threading

def get_html(url):
    try:
        url = url.encode('utf-8')
        page = urllib2.urlopen(url)
        return page.read()
    except Exception as ex:
        print 'get url_%s html error, ex=%s' % (url, ex)

def get_images(url):
    url = url.encode('utf-8')
    html = get_html(url)
    pattern = r'<img.+class="BDE_Image".+src="([^"]+\.jpg)"'
    img_list = re.findall(pattern, html)
    pattern = r'<img.+src="([^"]+\.jpg)".+class="BDE_Image"'
    img_list.extend(re.findall(pattern, html))
    # 去重
    img_list = sorted(set(img_list), key=img_list.index)
    return img_list

# 指定主题页面之总页面数
def get_page_count(url):
    html = get_html(url)
    pattern = r'"total_page":(\d+)'
    m = re.search(pattern, html)
    return m.group(1) if m else 0

# 获取每页主题url列表
def get_page_urls(html):
    pattern = r'<a href="/p/(\d+)"'
    url_list = re.findall(pattern, html)
    if url_list:
        url_list = map(lambda x: 'https://tieba.baidu.com/p/%s' % x, url_list)
    return url_list

# 下载指定页面之图片
def download_page_images(page_url):
    html = get_html(page_url)
    title = re.search(r'(?<=<title>)(.*)(?=</title>)', html).group(1)
    print title
    page_no = re.search(r'(\d+)', page_url).group(0)
    page_count = int(get_page_count(page_url))
    print 'page: %s, page_count: %d' % (page_no, page_count)

    for page_idx in range(1, page_count + 1):
        url = page_url + '?pn=%d' % page_idx
        img_list = get_images(url)
        if img_list:
            print 'page index: %d, image_count: %d' % (page_idx, len(img_list))
            if not os.path.exists('images'):
                os.mkdir('images')

            img_folder = 'images\%s' % page_no
            if not os.path.exists(img_folder):
                os.mkdir(img_folder)
            idx = 0
            for img_url in img_list:
                img_filename = img_folder + '\%d_%d.jpg' % (page_idx, idx)
                if not os.path.exists(img_filename):
                    urllib.urlretrieve(img_url, img_filename)
                idx += 1

def main():
    # 扒取最大页数
    max_pagecount = 30
    base_url = r'https://tieba.baidu.com/f?kw=图片&ie=utf-8?pn=%s'

    # 分页而扒
    for idx in range(1, max_pagecount):
        url = base_url % ((idx - 1) * 50)
        html = get_html(url)
        url_list = get_page_urls(html)
        for page_url in url_list:
            try:
                download_page_images(page_url)
                threading._sleep(2)
            except:
                continue

if __name__ == '__main__':
    main()