day15-2

一：json&pickle 模块

json 用于字符串和python数据类型进行转换。因为python中的数据类型不能写入文件，所以需要转换为字符串或者bytes存入文件中

pickle  用于python特有的数据类型和python的数据类型进行转换

json 提供四个功能，dumps，dump，loads，load

pickle.......               dumps，dump，loads，load

见前面笔记

二：shelve模块是一个简单的k，v 将内存数据持久化的一个模块，可以持久化任何pickle 可支持的python 数据类型

import shelve
import datetime
d = shelve.open('shelve_test1')
# time = datetime.datetime.now()
# person = {'name':'ri','sex':'man'}
# data = ['mon','sat','sun']
#
# d['time'] = time
# d['person'] = person
# d['data'] = data
# d.close()
# 将信息存入文件，生成三个文件 shelve_test1后缀分别为.bak .dat  .dir
print(d.get('time'))
print(d.get('person'))
print(d.get('data'))
d.close()

三：xml模块

 xml模块是实现不同语言或者程序之间进行数据交换的协议，和json类似，但json使用起来更加方便简单。在现在很多传统公司仍然使用xml较多

xml 通过 <>  <> 节点来区别数据结构

xml文件

<?xml version="1.0"?>
<softCompany>
    <company>MicroSoft</company>
    <name>yang</name>
    <age>99</age>
    <company>google</company>
    <sex>
        <p>男</p>
        <m>女</m>
    </sex>
    <company>Apple</company>
    <company>百度</company>
</softCompany>

xml模块读操作

# python处理xml
import xml.etree.ElementTree as ETX

tree = ETX.parse('xmltest.xml')
root = tree.getroot()
print(root)      # 返回地址
print(root.tag)  # 打印标签

# <Element 'softCompany' at 0x0000000000B57188>
# softCompany

# 遍历xml文档
for child in root:
    print(child.tag,child.text,child.attrib,'sss')
    for node in child:
        print(node.tag,node.attrib,node.text)
# 只遍历company节点
print('stop'.center(50,'-'))
for node in root.iter('company'):
    print(node.tag,node.attrib)
    
# <Element 'softCompany' at 0x0000000001167188>
# softCompany
# company MicroSoft {} sss
# name yang {} sss
# age 99 {} sss
# company google {} sss
# sex 
#          {} sss
# p {} 男
# m {} 女
# company Apple {} sss
# company 百度 {} sss
# -----------------------stop-----------------------
# company {}
# company {}
# company {}
# company {}

xml写操作

import xml.etree.ElementTree as ET
 
tree = ET.parse("xmltest.xml")
root = tree.getroot()
 
#修改
for node in root.iter('year'):
    new_year = int(node.text) + 1
    node.text = str(new_year)
    node.set("updated","yes")
 
tree.write("xmltest.xml")
 
 
#删除node
for country in root.findall('country'):
   rank = int(country.find('rank').text)
   if rank > 50:
     root.remove(country)
 
tree.write('output.xml')

创建

#修改和删除xml内容
import xml.etree.ElementTree as ET

new_xml = ET.Element("namelist")
name = ET.SubElement(new_xml, "name", attrib={"enrolled": "yes"})
age = ET.SubElement(name, "age", attrib={"checked": "no"})
sex = ET.SubElement(name, "sex")
sex.text = '男'
name2 = ET.SubElement(new_xml, "name", attrib={"enrolled": "no"})
age = ET.SubElement(name2, "age")
age.text = '19'

et = ET.ElementTree(new_xml)  # 生成文档对象
et.write("test.xml", encoding="utf-8", xml_declaration=True)

ET.dump(new_xml)  # 打印生成的格式