python 网络爬虫（慕课网）

代码：

##爬取网络：慕课网（"https://www.imooc.com/"）

from bs4 import BeautifulSoup
import urllib.request
import xlwt
import time

time_star = time.time()
ur = ["mobile","python","java","php"]  ##通过查看网页源代码，手动构造访问链接
url_basic, mingc, lianj, url, hda, x = [], [], [], [], [], 1

for j in range(len(ur)):
    url_basic.append("http://www.imooc.com/course/list?c=" + ur[j] +"&page=")
    for i in range(7): ##网页个数最多为7
        urll = url_basic[j] + str(i)
        url.append(urll) 


heads = {
     'Connection': 'keep-alive',
    'Accept-Language': 'zh-CN,zh;q=0.9',
     'Accept': 'text/html,application/xhtml+xml,application/xml;\
     q=0.9,image/webp,image/apng,*/*;q=0.8',
     'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36\
    (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36',
}

for key,value in heads.items():
    items = (key,value)
    hda.append(items)
    
opn = urllib.request.build_opener()
opn.addheaders = hda
urllib.request.install_opener(opn)

for i in url:
    try:  ##当网页不存在时，跳过本次循环，以便程序继续执行
        data = opn.open(i).read()
        soup = BeautifulSoup(data,'lxml')
        coursenames = soup.find_all('h3',class_="course-card-name")
        links = soup.find_all('a',class_="course-card")
    except:
        continue
    for cour in coursenames:
        coursenames = cour.get_text()
        mingc.append(coursenames)
        x += 1  
    for link in links:
        links = 'https://www.imooc.com'+str(link['href'])
        lianj.append(links)


header = ["序号","课程名称","课程链接"]
with open(r"C:\Users\AdamCY\Desktop\wenjian\python爬虫\py_spa.xlsx", "w",encoding='utf-8') as file:   
    file = xlwt.Workbook(encoding = 'utf-8')  
    sheet = file.add_sheet('hello')  
    sheet.write(0, 0, header[0]) ##此处尚需优化：学习用一行代码插入三列的标题（表头）
    sheet.write(0, 1, header[1])
    sheet.write(0, 2, header[2])
    for i in range(x-1):
        sheet.write(i+1, 0, i+1)
        sheet.write(i+1, 1, mingc[i])  
        sheet.write(i+1, 2, lianj[i])   
        file.save(r"C:\Users\AdamCY\Desktop\wenjian\python爬虫\py_spa.xlsx")

time_spend = time.time() - time_star
print(time_spend)  ##运行结果为32秒，代码执行速度太慢，还需要进一步优化

结果：