import requests, os, bs4

url = 'https://xkcd.com'
os.makedirs('xkcd',exist_ok = True)

while not url.endswith('#'):
    
    # download the page
    print('downloading the %s...'%(url))  # '%s...'%(url)對字串及進行替換
    res = requests.get(url)
    res.raise_for_status()   # 返回請求的狀態
    soup = bs4.BeautifulSoup(res.text, 'lxml')
    
    # find the url of the comic image
    comicele = soup.select('#comic img')
    print(comicele)
    if comicele == []:
        print('could not find comic image')
    else:
        comicurl = comicele[0].get('src')
        print(comicurl)
##        print('downloading image %s...'% (comicurl))
        res = requests.get(comicurl)
        res.raise_for_status()
    
    # download the image
    # save the image to ./xkcd

    imagefile = open(os.path.json('xkcd',os.path.basename(comicurl)), 'wb')
    for chunk in res.iter_content(100000):
        imagefile.write(chunk)
    imagefile.close()
    
    # get the prev button's url
    privelink = soup.select('a[rel = "prev"]')[0]
    url = 'https://xkcd.com' + prevlink.get('href')
print('DONE')