Python之多线程爬虫抓取网页图片的代码实例

import urllib.request

# ------ 伪装为浏览器 ---
def makeOpener(head={
  'Connection': 'Keep-Alive',
  'Accept': 'text/html, application/xhtml+xml, */*',
  'Accept-Language': 'zh-CN,zh;q=0.8,zh-TW;q=0.7,zh-HK;q=0.5,en-US;q=0.3,en;q=0.2',
  'Connection': 'keep-alive',
  'User-Agent':'Mozilla/5.0 (Windows NT 6.1; WOW64; rv:57.0) Gecko/20100101 Firefox/57.0'
  }):
  cj = http.cookiejar.CookieJar()
  opener = urllib.request.build_opener(urllib.request.HTTPCookieProcessor(cj))
  header = []
  for key, value in head.items():
    elem = (key, value)
    header.append(elem)
  opener.addheaders = header
  return opener

# ------ 获取网页源代码 ---
# url 网页链接地址
def getHtml(url):
  print('url='+url)
  oper = makeOpener()
  if oper is not None:
    page = oper.open(url)
    #print ('-----oper----')
  else:
    req=urllib.request.Request(url)
    # 爬虫伪装浏览器
    req.add_header('User-Agent','Mozilla/5.0 (Windows NT 6.1; WOW64; rv:57.0) Gecko/20100101 Firefox/57.0')
    page = urllib.request.urlopen(req)
  html = page.read()
  if collectHtmlEnabled: #是否采集html
    with open('html.txt', 'wb') as f:
      f.write(html) # 采集到本地文件，来分析
  # ------ 修改html对象内的字符编码为UTF-8 ------
  if chardetSupport:
    cdt = chardet.detect(html)
    charset = cdt['encoding'] #用chardet进行内容分析
  else:
    charset = 'utf8'
  try:
    result = html.decode(charset)
  except:
    result = html.decode('gbk')
  return result

# ------ 根据图片url下载图片 ------
# folderPath 定义图片存放的目录 imgUrl 一个图片的链接地址 index 索引，表示第几个图片
def downloadImg(folderPath, imgUrl, index):
  # ------ 异常处理 ------
  try:
    imgContent = (urllib.request.urlopen(imgUrl)).read()
  except urllib.error.URLError as e:
    if printLogEnabled : print ('【错误】当前图片无法下载')
    return False
  except urllib.error.HTTPError as e:
    if printLogEnabled : print ('【错误】当前图片下载异常')
    return False
  else:
    imgeNameFromUrl = os.path.basename(imgUrl)
    if printLogEnabled : print ('正在下载第'+str(index+1)+'张图片，图片地址:'+str(imgUrl))
    # ------ IO处理 ------
    isExists=os.path.exists(folderPath)
    if not isExists: # 目录不存在，则创建
       os.makedirs( folderPath )
       #print ('创建目录')
    # 图片名命名规则，随机字符串
    imgName = imgeNameFromUrl
    if len(imgeNameFromUrl) < 8:
      imgName = random_str(4) + random_str(1,'123456789') + random_str(2,'0123456789')+"_" + imgeNameFromUrl
    filename= folderPath + "\\"+str(imgName)+".jpg"
    try:
       with open(filename, 'wb') as f:
         f.write(imgContent) # 写入本地磁盘
       # if printLogEnabled : print ('下载完成第'+str(index+1)+'张图片')
    except :
      return False
    return True

# ------ 批量下载图片 ------
# folderPath 定义图片存放的目录 imgList 多个图片的链接地址
def downloadImgList(folderPath, imgList):
  index = 0
  # print ('poolSupport='+str(poolSupport))
  if not poolSupport:
   #print ('多线程模式')
   # ------ 多线程编程 ------
   threads = []
   for imgUrl in imgList:
     # if printLogEnabled : print ('准备下载第'+str(index+1)+'张图片')
     threads.append(threading.Thread(target=downloadImg,args=(folderPath,imgUrl,index,)))
     index += 1
   for t in threads:
     t.setDaemon(True)
     t.start()
   t.join() #父线程，等待所有线程结束
   if len(imgList) >0 : print ('下载结束，存放图片目录：' + str(folderPath))
  else:
   #print ('线程池模式')
    # ------ 线程池编程 ------
   futures = []
   # 创建一个最大可容纳N个task的线程池 thePoolSize 为 全局变量
   with concurrent.futures.ThreadPoolExecutor(max_workers=thePoolSize) as pool: 
    for imgUrl in imgList:
     # if printLogEnabled : print ('准备下载第'+str(index+1)+'张图片')
     futures.append(pool.submit(downloadImg, folderPath, imgUrl, index))
     index += 1
    result = concurrent.futures.wait(futures, timeout=None, return_when='ALL_COMPLETED')
    suc = 0
    for f in result.done:
      if f.result(): suc +=1
    print('下载结束，总数：'+str(len(imgList))+'，成功数：'+str(suc)+'，存放图片目录：' + str(folderPath))

# ------ 下载百度帖子内所有图片 ------
# folderPath 定义图片存放的目录 url 百度贴吧链接
def downloadImgFromBaidutieba(folderPath='tieba', url='https://tieba.baidu.com/p/5256331871'):
  html = getHtml(url)
  # ------ 利用正则表达式匹配网页内容找到图片地址 ------
  #reg = r'src="(.*?\.jpg)"'
  reg = r'src="(.*?/sign=.*?\.jpg)"'
  imgre = re.compile(reg);
  imgList = re.findall(imgre, html)
  print ('找到图片个数：' + str(len(imgList)))
  # 下载图片
  if len(imgList) >0 : downloadImgList(folderPath, imgList) 

# 程序入口
if __name__ == '__main__':
  now = datetime.datetime.now().strftime('%Y-%m-%d %H-%M-%S')
  # 下载百度帖子内所有图片
  downloadImgFromBaidutieba('tieba\\'+now, 'https://tieba.baidu.com/p/5256331871')