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from urllib.error import URLError

from urllib.request import urlopen

import re

import redis

import ssl

import hashlib

import logging

import pickle

import zlib

# Redis有两种持久化方案

# 1. RDB

# 2. AOF

# 通过指定的字符集对页面进行解码(不是每个网站都将字符集设置为utf-8)

def decode_page(page_bytes, charsets=('utf-8',)):

page_html = None

for charset in charsets:

try:

page_html = page_bytes.decode(charset)

break

except UnicodeDecodeError:

pass

# logging.error('[Decode]', err)

return page_html

# 获取页面的HTML代码(通过递归实现指定次数的重试操作)

def get_page_html(seed_url, *, retry_times=3, charsets=('utf-8',)):

page_html = None

try:

if seed_url.startswith('http://') or \

seed_url.startswith('https://'):

page_html = decode_page(urlopen(seed_url).read(), charsets)

except URLError as err:

logging.error('[URL]', err)

if retry_times > 0:

return get_page_html(seed_url, retry_times=retry_times - 1,

charsets=charsets)

return page_html

# 从页面中提取需要的部分(通常是链接也可以通过正则表达式进行指定)

def get_matched_parts(page_html, pattern_str, pattern_ignore_case=re.I):

pattern_regex = re.compile(pattern_str, pattern_ignore_case)

return pattern_regex.findall(page_html) if page_html else []

# 开始执行爬虫程序

def start_crawl(seed_url, match_pattern, *, max_depth=-1):

client = redis.Redis(host='1.2.3.4', port=6379, password='1qaz2wsx')

charsets = ('utf-8', 'gbk', 'gb2312')

logging.info('[Redis ping]', client.ping())

url_list = [seed_url]

visited_url_list = {seed_url: 0}

while url_list:

current_url = url_list.pop(0)

depth = visited_url_list[current_url]

if depth != max_depth:

page_html = get_page_html(current_url, charsets=charsets)

links_list = get_matched_parts(page_html, match_pattern)

for link in links_list:

if link not in visited_url_list:

visited_url_list[link] = depth + 1

page_html = get_page_html(link, charsets=charsets)

if page_html:

hasher = hashlib.md5()

hasher.update(link.encode('utf-8'))

zipped_page = zlib.compress(pickle.dumps(page_html))

client.set(hasher.hexdigest(), zipped_page)

def main():

ssl._create_default_https_context = ssl._create_unverified_context

start_crawl('http://sports.sohu.com/nba_a.shtml',

r'<a[^>]+test=a\s[^>]*href=["\'](.*?)["\']',

max_depth=2)

if __name__ == '__main__':

main()