Python crawls images based on keywords

'''
爬取指定关键字图片
'''
import re# 正则表达式，解析网页
import requests# 请求网页
import traceback
import os
 
    
def dowmloadPic(html,keyword,startNum):
    headers = {
    
    'user-agent':'Mozilla/5.0'}# 浏览器伪装，因为有的网站会反爬虫，通过该headers可以伪装成浏览器访问，否则user-agent中的代理信息为python
    pic_url = re.findall('"objURL":"(.*?)",',html,re.S)# 找到符合正则规则的目标网站
    num = len(pic_url)
    i = startNum
    subroot = root + '/' + word
    txtpath = subroot + '/download_detail.txt'

    print('找到关键词:'+keyword+'的图片，现在开始下载图片...')
    
    for each in pic_url:
        a = '第'+str(i+1)+'张图片，图片地址:'+str(each) + '\n'
        b = '正在下载' + a
        print(b)
        path = subroot + '/' + str(i+1)
        try:
            if not os.path.exists(subroot):
                os.mkdir(subroot)
            if not os.path.exists(path):
                pic = requests.get(each,headers = headers,timeout = 10)
                with open(path+'.jpg','wb') as f:
                    f.write(pic.content)
                    f.close()
                with open(txtpath,'a') as f:
                    f.write(a)
                    f.close()
                    
        except:
            traceback.print_exc()
            print ('【错误】当前图片无法下载')
            continue
        i += 1
 
    return i
 
 
if __name__ == '__main__':
    
    headers = {
    
    'user-agent':'Mozilla/5.0'}
    words = ['桃子','苹果','梨']
    #words为一个列表，可以自动保存多个关键字的图片
    root = './download_images_of_'
    for word in words:
        root = root + word + '&'
    if not os.path.exists(root):
        os.mkdir(root)
    for word in words:
        lastNum = 0
        # word = input("Input key word: ")
        if word.strip() == "exit":
            break
        pageId = 0
        #此处的参数为需爬取的页数，设置为2页
        for i in range(3):
            url = 'http://image.baidu.com/search/flip?tn=baiduimage&ie=utf-8&word=' + word + "&pn="+str(pageId)+"&gsm=?&ct=&ic=0&lm=-1&width=0&height=0"
            pageId += 20#好像没啥影响
            html = requests.get(url,headers = headers)
            # print(html.text) #打印网页源码，相当于在网页中右键查看源码内容
            lastNum = dowmloadPic(html.text, word, lastNum,)#本条语句执行一次获取60张图