结合Selenium和正则表达式提高爬虫效率
用Selenium爬取aliexpress的商品信息
任务
爬取https://www.aliexpress.com/wholesale?SearchText=cartoon+case&d=y&origin=n&catId=0&initiative_id=SB_20200523214041这个页面下的商品详情，由于页面是异步加载的，需要使用Selenium模拟浏览器来获取商品url。但直接使用Selenium定位网页元素速度又很慢，因此需要结合Re或者BeautifulSoup来提高爬取效率。
模拟登陆
使用Selenium模拟登录，登录成功后获取cookie。
def login(username, password, driver=None): driver.get('https://login.aliexpress.com/') driver.maximize_window() name = driver.find_element_by_id('fm-login-id') name.send_keys(username) name1 = driver.find_element_by_id('fm-login-password') name1.send_keys(password) submit = driver.find_element_by_class_name('fm-submit') time.sleep(1) submit.click() return driverbrowser = webdriver.Chrome()browser = login('Wheabion1944@dayrep.com','ab123456',browser)browser.get('https://www.aliexpress.com/wholesale?trafficChannel=main&d=y&SearchText=cartoon+case<ype=wholesale&SortType=default&page=')这个网站对用户监管不严，使用邮箱注册都不需要进行验证，可以用这个网站获取假邮箱进行注册：其实后续真正运行程序爬的时候并没有登录，爬了十页也没碰到反爬。
获取商品详情页的URL
这一过程需要解决的问题在于该网页是ajex异步加载的，网页不会在打开的同时加载全部数据，在下拉的同时网页刷新返回新的数据包并渲染，因此通过request无法一次性读到网页的全部源码。解决思路是通过Selenium来模拟浏览器下拉行为以获取一页内全部的数据，然后暂时还是通过sel去获取元素。
登录后打开任务需要的页面会出现广告弹窗，首先需要关闭广告弹窗：
def close_win(browser): time.sleep(10) try: closewindow = browser.find_element_by_class_name('next-dialog-close') browser.execute_script("arguments[0].click();", closewindow) except Exception as e: print(f"searchKey: there is no suspond Page1. e = {e}")模拟下拉行为并获取一页中全部商品的url：
def get_products(browser): wait = WebDriverWait(browser, 1) for i in range(30): browser.execute_script('window.scrollBy(0,230)') time.sleep(1) products = wait.until(EC.presence_of_all_elements_located((By.CLASS_NAME,"product-info"))) if len(products) >= 60: break else: print(len(products)) continue products = browser.find_elements_by_class_name('product-info') return products
获取商品内页详情
这一部分的问题在于需要爬取的网页很多，继续使用sel会导致爬虫速度很慢，另外商品内页的数据似乎不是异步返回的。解决方案是先使用sel访问商品内页，将整个网页源码down下来后用正则表达式去匹配元素：
def get_pro_info(product): url = product.find_element_by_class_name('item-title').get_attribute('href') driver = webdriver.Chrome() driver.get(url) page = driver.page_source driver.close() material=re.findall(r'"skuAttr":".*?#(.*?);',page) color=re.findall(r'skuAttr":".*?#.*?#(.*?)"',page) stock=re.findall(r'skuAttr":".*?"availQuantity":(.*?),',page) price=re.findall(r'skuAttr":".*?"actSkuCalPrice":"(.*?)"',page) pics = re.findall(r'<div ><img src="(.*?)"', page) titles = re.findall(r'<img src=".*?" title="(.*?)">', page) video = re.findall(r'id="item-video" src="(.*?)"', page) return material, color, stock, price, pics, titles, video
接入MySQL
爬取到的数据要求用数据库储存，这里需要接入MySQL，数据库crawl和表SKU都是提前建好的：
conn = pymysql.connect(host='localhost', user='root', password='ab226690',db='crawl')
mycursor = conn.cursor()
通过循环实现数组数据的写入，这里很坑的一点是insert的时候pymysql的格式转换和python不是完全一样，参数用'%s'匹配就可以，不需要针对数字型字段搞整形或浮点型：
#写入sku表 sql = "INSERT INTO SKU(skuID,material,color,stock,price, url) VALUES (%s,%s,%s,%s,%s,%s)"#就是这里，虽然有些变量是数值型，但还是用%s来对应 for i in range(len(skuID)): if titles: params = (skuID[i], material[i], color[i], stock[i], price[i],url) else: params = (skuID[i], material[i], ' ', stock[i], price[i],url) try: mycursor.execute(sql,params) conn.commit() except IntegrityError: #当出现duplicate primary key时会抛出这个错误，这里这样写的本意是碰到重复主键就跳过这一条记录，但实际运行这段代码的时候还是会报错。偷懒的解决办法是把主键取消，但这样好像不是很合理，日后知道怎么解决再来更新 conn.rollback() continue
实现写入操作时碰到的另一个问题是用re匹配不到元素时返回的是一个空的list，这样会导致无法写入mysql而报错，因此要判断待写入的变量是否是空的list，是的话要赋合适的值：
sql = "INSERT INTO product(url, product_name, rating, reviews, video, shipping) VALUES (%s,%s,%s,%s,%s,%s)" if rating: pass else: rating = '0.0' if review: pass else: review = '0' if video: pass else: video = ' ' if shipping: pass else: shipping = '0.0' params = (url, pro_name, rating,review, video, shipping) mycursor.execute(sql,params)
关闭数据库连接：
conn.commit()
提升速度
除了前面提到的使用selenium访问后转用re匹配外，还发现一个提升爬虫效率的点：
browser = webdriver.Chrome()browser.get(source_url)browser = close_win(browser)
像这样重复地实例化和关闭浏览器驱动是很耗费时间的，因此要使用尽量少的浏览器窗口来访问网站。
本任务中是只实例化了两个webdriver，一个用来访问多个商品的展示页，一个用来访问商品内页，具体方法就是实例化后不要这两个driver，一直用它们来get新的网页。原来的代码中是每打开一个网页都初始化一个新的webdriver去访问，做出这一修改后代码运行时间减少了一半。
def scratch_page(source_url): browser = webdriver.Chrome() browser.get(source_url) browser.maximize_window() browser = close_win(browser) pros = get_products(browser) #商品内页的浏览器 browser2 = webdriver.Chrome() error_file = open('ERROR.txt','a+',encoding='utf8') for pro in pros: url, pro_name, skuID, material, color, stock, price, pics, titles, video,rating,shipping, review = get_pro_info(pro, browser2)#对前面的get_pro_info
做简单修改 if len(skuID)!=len(color): error_file.write('url:'+url+'\n') continue save_data_to_sql(url,pro_name, skuID, material, color, stock, price, pics, titles, video,rating,shipping,review) error_file.close() browser.close() browser2.close()
完整代码
from selenium import webdriverimport time from selenium.webdriver.common.by import Byfrom selenium.webdriver.support.ui import WebDriverWaitfrom selenium.webdriver.support import expected_conditions as ECimport reimport pymysqlfrom sqlalchemy.exc import IntegrityError#捕获重复主键的异常def login(username, password, driver=None): driver.get('https://login.aliexpress.com/') driver.maximize_window() name = driver.find_element_by_id('fm-login-id') name.send_keys(username) name1 = driver.find_element_by_id('fm-login-password') name1.send_keys(password) submit = driver.find_element_by_class_name('fm-submit') time.sleep(1) submit.click() return driverdef close_win(browser): time.sleep(5) try: closewindow = browser.find_element_by_class_name('next-dialog-close') closewindow.click() except Exception as e: print(f"searchKey: there is no suspond Page1. e = {e}") return browserdef get_products(browser): wait = WebDriverWait(browser, 1) for i in range(30): browser.execute_script('window.scrollBy(0,230)') time.sleep(1) products = wait.until(EC.presence_of_all_elements_located((By.CLASS_NAME,"product-info"))) if len(products) >= 60: break else: continue products = browser.find_elements_by_class_name('product-info') return productsdef get_pro_info(product, driver): url = product.find_element_by_class_name('item-title').get_attribute('href') driver.get(url) time.sleep(0.5) page = driver.page_source material=re.findall(r'"skuAttr":".*?#(.*?);',page) color=re.findall(r'"skuAttr":".*?#.*?#(.*?)"',page) stock=re.findall(r'"skuAttr":".*?"availQuantity":(.*?),',page) price=re.findall(r'"skuAttr":".*?"skuCalPrice":"(.*?)"',page) pics = re.findall(r'<div ><img src="(.*?)"', page) titles = re.findall(r'<img src=".*?" title="(.*?)">', page) video = re.findall(r'id="item-video" src="(.*?)"', page) skuID = re.findall(r'"skuId":(.*?),',page) pro_name = re.findall(r'"product-title-text">(.*?)</h1>', page) rating = re.findall(r'itemprop="ratingValue">(.*?)</span>', page) shipping = re.findall(r'<span >(.*?) ', page) review = re.findall(r'"reviewCount">(.*?) Reviews</span>', page) #当商品没有颜色可选时，网页源码结构变化，需要重新匹配 if titles: pass else: material = re.findall(r'"skuAttr":".*?#(.*?)"', page) color=[] pics = re.findall(r'"imagePathList":\["(.*?)",', page) return url, pro_name, skuID, material, color, stock, price, pics, titles, video,rating,shipping, review def save_data_to_sql(url,pro_name, skuID, material, color, stock, price, pics, titles, video,rating,shipping,review): url = re.findall('/item/(.*?).html',url)# try: conn = pymysql.connect(host='localhost', user='root', password='ab226690',db='crawl') mycursor = conn.cursor() #写入sku表 sql = "INSERT INTO SKU(skuID,material,color,stock,price, url) VALUES (%s,%s,%s,%s,%s,%s)" for i in range(len(skuID)): if titles: params = (skuID[i], material[i], color[i], stock[i], price[i],url) else: params = (skuID[i], material[i], ' ', stock[i], price[i],url)# mycursor.execute(sql,params)# conn.commit() try: mycursor.execute(sql,params) conn.commit() except IntegrityError: conn.rollback() continue #写入img表 sql = "INSERT INTO image(url, color, img) VALUES (%s,%s,%s)" i = 0 if titles: for i in range(len(titles)): params = (url, titles[i], pics[i])# mycursor.execute(sql,params)# conn.commit() try: mycursor.execute(sql,params) conn.commit() except IntegrityError: conn.rollback() continue else: params = (url, ' ', pics)# mycursor.execute(sql,params)# conn.commit() try: mycursor.execute(sql,params) conn.commit() except IntegrityError: conn.rollback() #写入product表 sql = "INSERT INTO product(url, product_name, rating, reviews, video, shipping) VALUES (%s,%s,%s,%s,%s,%s)" if rating: pass else: rating = '0.0' if review: pass else: review = '0' if video: pass else: video = ' ' if shipping: pass else: shipping = '0.0' params = (url, pro_name, rating,review, video, shipping) mycursor.execute(sql,params) conn.commit()# try:# mycursor.execute(sql,params)# conn.commit()# except Exception:# conn.rollback() conn.close()# except Exception as e:# conn.rollback()# print(e) def scratch_page(source_url): browser = webdriver.Chrome() browser.get(source_url) browser.maximize_window() browser = close_win(browser) pros = get_products(browser) #商品内页的浏览器 browser2 = webdriver.Chrome() error_file = open('ERROR.txt','a+',encoding='utf8') for pro in pros: url, pro_name, skuID, material, color, stock, price, pics, titles, video,rating,shipping, review = get_pro_info(pro, browser2) if len(skuID)!=len(color): error_file.write('url:'+url+'\n') continue save_data_to_sql(url,pro_name, skuID, material, color, stock, price, pics, titles, video,rating,shipping,review) error_file.close() browser.close() browser2.close() url = 'https://www.aliexpress.com/wholesale?trafficChannel=main&d=y&SearchText=cartoon+case<ype=wholesale&SortType=default&page='for p in range(1,11): url_ = url + str(p) start_time = time.time() scratch_page(url_) end_time = time.time() print('成功爬取' + str(p) + '页') print('第' + str(p) + '页耗时： '+str(start_time-end_time)+'s')
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