利用 Python 编写简单网络爬虫实例 2

实验环境

python 版本：3.3.5

实验目的

获取目标网站“http://www.51testing.com/html/index.html”中特定 url，通过分析发现，目标 url 同其它 url 的关系如下 ：

目标 url 存在子页面中的文章中，随机分布，我们要把它找出来

python 脚本

#!/usr/bin/env python

# -*- coding:utf-8 -*-

from urllib.request import *

import gzip, re

from io import BytesIO

from html.parser import HTMLParser

# 爬虫类

class Reptile:

"""to download web pages"""

def __init__(self):

self.url_set = set() # 用于存储已下载过的页面 url

self.data = ""

# 下载网页

def get_page(self, url, headers):

request = Request(url, headers=headers)

request.add_header('Accept-encoding', 'gzip') #下载经过 gzip 方式压缩后的网页，减少网络流量

try:

response = urlopen(request) # 发送请求报文

if response.code == 200: # 请求成功

page = response.read() # 读取经压缩后的页面

if response.info().get("Content-Encoding") == "gzip":

page_data = BytesIO(page)

gzipper = gzip.GzipFile(fileobj = page_data)

self.data = gzipper.read()

else:

print("gzip unused")

self.data = page_data # 网页未采用 gzip 方式压缩，使用原页面

except Exception:

pass

self.url_set.add(url)

return self.data

# 获取网站入口版块的 url

def get_board_url(self, url_set, include):

board_url_set = set() # 用于存放版块 url

while len(url_set) > 0:

url = url_set.pop()

if re.findall(include, url):

board_url_set.add(url)

return board_url_set

# 转换后 URL:http://www.51testing.com/html/90/category-catid-90.html

# 入口版块及其子版块 url 转换

def convert_board_url(self, url_set, if_sub=False):

tmp_url_set = set()

for url in url_set:

str1 = re.findall("[?].+[\d]+", url)

str2 = re.findall("[?].+[-_]+", url) # 存放 url 中需要被替换的字符串

if str1[0][-2:].isdigit():

var = str1[0][-2:]

else:

var = str1[0][-1:]

replace_str = "html/"+var+"/category-catid-"

url_new = url.replace("".join(str2), replace_str)

if if_sub: # 如果为子版块，需要添加.html 结尾字符串

url_new = url_new + ".html"

tmp_url_set.add(url_new)

return tmp_url_set

# 转换后 URL:http://www.51testing.com/html/91/category-catid-91-page-2.html

# 转换子版块下子页面的 url

def convert_sub_page_url(self, url_set):

tmp_url_set = set()

for url in url_set:

str1 = re.findall("[?].+-catid-[\d]+", url)

str2 = re.findall("[?].+[-_]catid", url) # 存放 url 中需要被替换的字符串

if str1[0][-2:].isdigit():

var = str1[0][-2:]

else:

var = str1[0][-1:]

replace_str = "html/"+var+"/category-catid"

url_new = url.replace("".join(str2), replace_str)

url_new = url_new + ".html"

tmp_url_set.add(url_new)

return tmp_url_set

# 获取 web 页面 url 下的帖子 url

def get_title_url(self, url_set, include):

title_url_set = set() # 用于存放帖子 url

while len(url_set) > 0:

url = url_set.pop()

if re.findall(include, url):

title_url_set.add(url)

return title_url_set

# 帖子，转换前 URL：

# 转换帖子 url： http://www.51testing.com/html/58/n-1262758.html

def conver_tilte_url(self, url_set):

tmp_url_set = set()

for url in url_set:

str1 = re.findall("[?].+[\d]+", url)

str2 = re.findall("[?].+[-_]+", url) # 存放 url 中需要被替换的字符串

if str1[0][-2:].isdigit():

var = str1[0][-2:]

else:

var = str1[0][-1:]

replace_str = "html/"+var+"/n-"

url_new = url.replace("".join(str2), replace_str)

url_new = url_new + ".html"

tmp_url_set.add(url_new)

return tmp_url_set

# 解析器类

class MyHtmlParser(HTMLParser):

def reset(self):

HTMLParser.reset(self) # 注意顺序

self.url_set = set()

def handle_starttag(self, tag, attrs):

#self.url = []

url_list = [value for key, value in attrs if "href" == key]

if url_list:

for url in url_list:

self.url_set.add(url)

##############测试################

# 添加头域，伪装浏览器访问网站,防止一些网站拒绝爬虫访问

headers = {'User-Agent':"Mozilla/5.0 (Windows NT 6.1; WOW64; rv:33.0) Gecko/20100101

Firefox/33.0"}

init_url = "http://www.51testing.com/html/index.html"

# 构造解析器

parser = MyHtmlParser(strict = False)

# 下载网页

print("program is downloading the frist url page")

reptile = Reptile()

page = reptile.get_page(init_url, headers)

print("processing the first url page")

# 解析网页(获取 url)

parser.feed(str(page))

# 获取入口版块 url

include = re.compile(pattern)

board_url_set = reptile.get_board_url(parser.url_set, include)

# 转换入口版块 url

board_url_set_new = reptile.convert_board_url(board_url_set)

# 获取每个入口版块下的子版块 url("更多"页面)

include = re.compile(pattern)

sub_board_url_set = set()

board_index = 1

for board_url in board_url_set_new:

page = reptile.get_page(board_url, headers)

parser.feed(str(page))

print("getting subboard urls in the %dth web board page" % board_index)

tmp_url_set = reptile.get_board_url(parser.url_set, include)

board_index = board_index + 1

sub_board_url_set = sub_board_url_set ^ tmp_url_set

# 转换入口版块的子版块的 url

sub_board_url_set_new = reptile.convert_board_url(sub_board_url_set, True)

#for url in sub_board_url_set_new:

# print(url)

# 获取子版块的子页面 url(点击数字页号翻页后的"页面",默认为前 10 页)

include = re.compile(pattern)

sub_page_url_set = set()

board_index = 1

for sub_page_url in sub_board_url_set_new:

page = reptile.get_page(sub_page_url, headers)

parser.feed(str(page))

print("getting sub page urls in the %dth web page" % board_index)

tmp_url_set = reptile.get_board_url(parser.url_set, include)

board_index = board_index + 1

sub_page_url_set = sub_page_url_set ^ tmp_url_set

#for url in sub_page_url_set:

# print(url)

# 转换子版块下的子页面 url

sub_page_url_set = reptile.convert_sub_page_url(sub_page_url_set)

# 获取所有 web 页面

web_page_set = sub_board_url_set_new ^ sub_page_url_set

# 获取页面文章

title_url_set = set()

board_index = 1

title_index = 1

for page_url in web_page_set:

page = reptile.get_page(page_url, headers)

parser.feed(str(page))

# 获取每个 web 页面下帖子 url

include = re.compile(pattern)

print("getting all title urls in the %dth web board" % board_index)

tmp_url_set = reptile.get_title_url(parser.url_set, include)

board_index = board_index + 1

title_url_set = title_url_set ^ tmp_url_set

title_url_set_new = reptile.conver_tilte_url(title_url_set)

# 获取每篇文章下的目标 url 并写入文件

target_index = 1

title_index = 1

filepath = "d:/url2.txt"

for title_url in title_url_set_new:

print("processing the %dth title url" % title_index)

page = reptile.get_page(title_url, headers)

parser.feed(str(page))

# 保存目标 url

with open(filepath, "a") as f:

while len(parser.url_set) > 0:

url = parser.url_set.pop()

pattern = "http://bbs.51testing.com/treasure/treasure.php[?]trenum=[0-9]"

include = re.compile(pattern)

flag = re.findall(include, url)

if flag:

print("find target! saving the %dth target url in the %dth title page" %

(target_index, title_index))

f.write("the %dth url: %s" % (target_index, url))

target_index = target_index + 1

f.write("\n")

title_index = title_index + 1

print("----------------complete-------------------")

结果：

声明：仅供学习研究使用，请勿用于其它非法用途。