PY__09

python

io
1. w写入重复执行之前的内容会被覆盖

my_string='hello world26,'
a=open('data01.txt','w')   # 建立一个a通道
a=open('data01.txt','a')      不会被覆盖
a.write(my_string)  # 将my_string字符串写入到data01.txt中

2.r读出

my_string='hello world26,'
b=open('data02.txt','r')
con=b.read()  # 读出内容
print(con)

3.w+可写可读优先执行写

b=open('data01.txt','w+')
b.write(my_string)  #将my_string写入
           #加上b.seek(0)可以读出，光标被提前
con=b.read()
print(con)  #此时读不出内容 因为光标在最后

4.wb 以字节码写入

a=open('data01.txt','wb')
a.write(my_string) #出错
a.write(my_string.encode())  #正常写入，内容还是原内容不是字节码

5.rb 以字节码读出

a=open('data01.txt','rb')
print(c)         # 输出字节码
print(c.decode())  #正常读出

6.json.dumps()#将python对象转化为json字符串

json.loads()#将json字符串转化为python对象

import json
users=[
    {"id":'0013中国',"user_name":"admin","user_password":"123","birthday":"20180-3-1"},
    {"id":'002',"user_name":"test","user_password":"123","birthday":"2012-4-1"},
    {"id":'003',"user_name":"boss","user_password":"666","birthday":"2007-5-1"}
]
s=json.dumps(users)  将字典转化为json字符串写入
fp=open('a.txt','w')
fp.write(s)

a=open('a.txt','r')
con=json.loads(a)
print(con)  读出
 =======================
 这样读出若有中文会出现字节码
           b=open('a.txt','r')
           c=b.read()
           print(c)

6.json序列化

  import json
  users=[
    {"id":'001',"user_name":"admin","user_password":"123","birthday":"20180-3-1"},
    {"id":'002',"user_name":"test","user_password":"123","birthday":"2012-4-1"},
    {"id":'003',"user_name":"boss","user_password":"666","birthday":"2007-5-1"}
]
 a=open('a.json','w')
 json.dump(users,a)   将json序列化写入

 b=open('a.json','r')
 con=json.load(b)  将json反序列化读出
 print(con)
 ```
  7.目录  ./当前目录 ../上一级目录
 ```
  import json
  users=[
    {"id":'001',"user_name":"admin","user_password":"123","birthday":"20180-3-1"},
    {"id":'002',"user_name":"test","user_password":"123","birthday":"2012-4-1"},
    {"id":'003',"user_name":"boss","user_password":"666","birthday":"2007-5-1"}
]
 fp=open('./w.txt','w')  写在当前目录下
 json.dump(users,fp)

 fp=open('./../w.txt','w') 写在上一级目录下
 json.dump(users,fp)

8.生成文件名不同的文件

import time
import random

my_time=time.time()
number=random.random()

file_name=my_time+number 将时间戳与随机数之和作为文件名，避免重名
a=open('./../'+str(file_name)+'.txt','w')
a.write() 会生成许多不同文件名的文件

8.flush() 缓冲

若写入两个文件在中间使用flush将上面的文件送走
import json
users=[
    {"id":'001',"user_name":"admin","user_password":"123","birthday":"20180-3-1"},
    {"id":'002',"user_name":"test","user_password":"123","birthday":"2012-4-1"},
    {"id":'003',"user_name":"boss","user_password":"666","birthday":"2007-5-1"}
]
a=open('q.json','w')
json.dump(users,a)

list=[1,2,3,4]
a.flush()
json.dump(list,a)

9.readline 按行读

 a=open('1.txt','r')
c=a.readline() 读出第一行 1
c=a.readline()  读出第二行 2
print(c)
print(a.tell())
c=a.readlines() 一行读出['1\n', '2\n', '3\n', '4']

10.内存读写

 #写入内存 临时存储在取出来 省掉定义变量

from io import StringIO,BytesIO
my_str='abcdefg'
fp=StringIO()
fp.write(my_str[::-1])#存入内存
str=my_str+fp.getvalue()#取出来
print(str)

BytesIO以二进制写入
fp_btye=BytesIO()
fp_btye.write('中国'.encode())#转化成字节码存入
print(fp_btye.getvalue())  #b'\xe4\xb8\xad\xe5\x9b\xbd'
print(fp_btye.getvalue().decode())#中国 解码输出

python

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