python爬虫项目设置一个中断重连的程序的实现

class UrlManager(object):
  def __init__(self):  #定义两个数组
    self.new_urls=set()
    self.old_urls=set()

  def add_new_url(self, url): #将一个url加入到new_urls数组中
    if url is None:
      return
    if url not in self.new_urls and url not in self.old_urls:
      self.new_urls.add(url)

  def add_new_urls(self, urls): #将多个url加入到new_urls数组中
    if urls is None or len(urls)==0:
      return
    for url in urls :
      self.add_new_url(url)

  def has_new_url(self):  #判断url是否为空
    return len(self.new_urls)!=0

  def get_new_url(self):
    #list.pop()默认移除列表中最后一个元素对象
    new_url=self.new_urls.pop()
    self.old_urls.add(new_url)
    return new_url

class UrlManager(object):
  def __init__(self):   #建立两个数组的文件
    with open('new_urls.txt','r+') as new_urls:
      self.new_urls = new_urls.read()
    with open('old_urls.txt','r+') as old_urls:
      self.old_urls = old_urls.read()

  def add_new_url(self, url):   #添加url到new_ulrs文件中
    if url is None:
      return
    if url not in self.new_urls and url not in self.old_urls:
      with open('new_urls.txt', 'a') as new_urls:
        new_urls.write(url)
    else:
      print('url had done')

  def add_new_urls(self, urls):  #添加多个url到new_ulrs文件中
    # if urls is None or (len(url) == 0 for url in urls):
    if urls is None:
      print('url is none')
      return
    for url in urls:
      if urls is None:
        print('url is none')
        return
      else:
        self.add_new_url(url)

  def has_new_url(self):
    return len(self.new_urls) != 0

  def get_new_url(self):  
    new_url = get_last_line('new_urls.txt')  #读取new_urls文件中最后一个url
    del_last_url('new_urls.txt',new_url) #删除new_urls文件中最后一个url
    add_old_urls('old_urls.txt',new_url) #将读取出来的url添加入old_urls数组中
    return new_url

import os
def get_last_line(inputfile):
  filesize = os.path.getsize(inputfile)
  blocksize = 1024
  dat_file = open(inputfile, 'rb')

  last_line = b""
  lines = []
  if filesize > blocksize:
    maxseekpoint = (filesize // blocksize) # 这里的除法取的是floor
    maxseekpoint -= 1
    dat_file.seek(maxseekpoint * blocksize)
    lines = dat_file.readlines()
    while ((len(lines) < 2) | ((len(lines) >= 2) & (lines[1] == b'\r\n'))): # 因为在Windows下，所以是b'\r\n'
      # 如果列表长度小于2，或者虽然长度大于等于2，但第二个元素却还是空行
      # 如果跳出循环，那么lines长度大于等于2，且第二个元素肯定是完整的行
      maxseekpoint -= 1
      dat_file.seek(maxseekpoint * blocksize)
      lines = dat_file.readlines()
  elif filesize: # 文件大小不为空
    dat_file.seek(0, 0)
    lines = dat_file.readlines()
  if lines: # 列表不为空
    for i in range(len(lines) - 1, -1, -1):
      last_line = lines[i].strip()
      if (last_line != b''):
        break # 已经找到最后一个不是空行的
  dat_file.close()
  return last_line

def del_last_url(fname,part):
  with open(fname,'rb+') as f:
    a = f.read()
  a = a.replace(part,b'')
  with open(fname,'wb+') as f:
    f.write(a)
    
def add_old_urls(fname,new_url):
  line = new_url + b'\r'
  with open(fname,'ab') as f:
    f.write(line)