Python，破解zip密码这个程序为什么老是出错？谁能帮我改一改？

#破解英文+数字型的密码
import random,zipfile,time,sys

class MyIter():
  cset = 'abcdefghijklmnopqrstuvwxyz0123456789'
  def __init__(self,min,max):#迭代器实现初始方法，传入参数
    if min < max:
      self.minlen = min
      self.maxlen = max
    else:
      self.ninlen = max
      self.maxlen = min
  def __iter__(self):#直接返回slef实列对象
    return self
  def __next__(self):#通过不断地轮循，生成密码
    rec = ''
    for i in range(0,random.randrange(self.minlen,self.maxlen+1)):
      rec += random.choice(MyIter.cset)
    return rec
def extract():
  start_time = time.time()
  zfile = zipfile.ZipFile(r'C:\Users\ASUS\Desktop\Python无师自通书籍与源码.zip')#路径
  for password in MyIter(1,4):#随机迭代出1~4位数的密码，在不明确位数的时候做相应的调整
    if zfile:
      try:
        zfile.extractall(path='.',pwd=str(password).encode('utf-8'))
        print ("当前压缩密码为：",password)
        end_time = time.time()
        print ('当前破解压缩包花了%s秒'%(end_time-start_time))
        sys.exit(0)
      except Exception as e:
        print ('pass密码：',password)
        pass
if __name__=="__main__":
  extract()

 #zfile = zipfile.ZipFile(r'C:\Users\ASUS\Desktop\Python无师自通书籍与源码.zip')#路径

 zfile = zipfile.ZipFile('C:\Users\ASUS\Desktop\Python无师自通书籍与源码.zip','r')#路径