text: import os
  import re
  import urllib.parse
  import urllib.request
         
  def download_files(first_url, output_dir):
      if not os.path.isdir(output_dir):
          os.mkdir(output_dir)
      url_head, url_tail = os.path.split(first_url)
      first_index = re.findall(r'[0-9]+', url_tail)[-1]
      index_count, error_count = 0, 0
      while(error_count < 5):
          next_index = str(int(first_index) + index_count)
          if first_index[0] == '0': # zero padded
              next_index = '0' * (len(first_index) - len(next_index)) + next_index
          next_url = urllib.parse.urljoin(url_head, re.sub(first_index, next_index, url_tail))
          try:
              output_file = os.path.join(output_dir, os.path.basename(next_url))
              urllib.request.urlretrieve(next_url, output_file)
              print('Successfully downloaded {}'.format(os.path.basename(next_url)))
          except IOError:
              print('Could not retrieve {}'.format(next_url))
              error_count += 1
          index_count += 1        
      
  if __name__ == '__main__':
      download_files('http://699340.youcanlearnit.net/image001.jpg', '.\\images')