def division(numerator,denominator):
  result=numerator/denominator
  return result
    
ret1=division(1,5)
print(ret1)

ret2=division(1,0)
print(ret2)

def division(numerator,denominator):
  try:
    result=numerator/denominator
    return result
  except ZeroDivisionError:
    return "denominator can not be zero"
  except BaseException:
    return "pls check if the numerator and denominator is number."
  else:
    return "unknow error"
      
ret1=division(1,5)
print(ret1)

ret2=division(1,0)
print(ret2)

def division(numerator,denominator):
  try:
    result=numerator/denominator
  except ZeroDivisionError:
    result = "denominator can not be zero"
  except BaseException:
    result = "pls check if the numerator and denominator is number."
  else:
    result = "unknow error"
  return result
    
ret1=division(1,5)
print(ret1)

ret2=division(1,0)
print(ret2)

import json
filename="myjson.json"
with open(filename,'w') as wr:
  json.dump([1,2,3,4],wr)

import json
filename="myjson.json"
with open(filename) as re:
  ls=json.load(re)


print(ls)

import json
import os
import time
import sys
import traceback
def login():
  json_file="./username.json"
  while(True):
    name=input("pls input your name: ")
    if "quit" == name:
      sys.exit(0)
    curr_time=time.strftime('%Y-%m-%d %H:%M:%S',time.localtime(time.time()))
    user_dict_list=[]
    if os.path.exists(json_file):
      with open(json_file) as jf:
        try:
          # 文件内容为空，或者文件内容，或者不符合json格式，所以此处添加异常处理
          user_dict_list=json.load(jf)
          isExist=False
          for ele in user_dict_list:
            username=ele.get("username")
            if username == name:
              isExist=True
              ele["lastLoginTime"]=curr_time
              print ("welcome back: %s, last login : %s"%(name,curr_time))
              break;
        
          if isExist == False:
            # 文件存在，且内容格式正确，但不存在当前用户
            first_login(user_dict_list,name,curr_time)
        except Exception:
          # 打印出异常信息，便于调测程序，正式使用事可以去掉，或者打印在后台，不给用户看到
          traceback.print_exc()
          #文件内容为空，或者文件内容格式不符合JSON要求
          first_login(user_dict_list,name,curr_time)
    else:
      # 文件不存在
      first_login(user_dict_list,name,curr_time)
    # 将用户信息写入/重新写入到文件中
    with open(json_file,'w') as jf:
      json.dump(user_dict_list,jf)
    
''' 将用户第一次登陆信息存放到集合中 '''
def first_login(user_dict_list,name,curr_time):
  my_dict={"username":name,"lastLoginTime":curr_time}
  user_dict_list.append(my_dict)
  print ("welcome: %s, have a nice day."%(name))
  
login()