shelve模块和xml模块

Posted 2020-10-30 Ryansuperwa

shelve模块

shelve模块比pickle模块简单，只有一个open，返回类似字典的对象，可读可写：key必须为字符串，

而值可以是python所支持的数据类型

import shelve
f=shelve.open(r‘shelve.txt‘)
 f[‘stu1_info‘]={‘name‘:‘egon‘,‘age‘:18,‘hobby‘:[‘piao‘,‘smoking‘,‘drinking‘]}
 f[‘stu2_info‘]={‘name‘:‘gangdan‘,‘age‘:53}
 f[‘school_info‘]={‘website‘:‘http://www.pypy.org‘,‘city‘:‘beijing‘}
print(f[‘stu1_info‘][‘hobby‘])
f.close()

 xml模块

xml是实现不同语言或者程序之间进行数据交换的协议，跟json差不多，但是json使用起来更简单，不过、

，古时候，在json还没诞生的黑暗年代，大家只能选择用xml呀，至今很多传统公司如金融行业的很多系统

的接口还主要是xml

xml的格式如下，就是通过<>节点来区别数据结构的：

<?xml version="1.0"?>
<data>
    <country name="Liechtenstein">
        <rank updated="yes">2</rank>
        <year>2008</year>
        <gdppc>141100</gdppc>
        <neighbor name="Austria" direction="E"/>
        <neighbor name="Switzerland" direction="W"/>
    </country>
    <country name="Singapore">
        <rank updated="yes">5</rank>
        <year>2011</year>
        <gdppc>59900</gdppc>
        <neighbor name="Malaysia" direction="N"/>
    </country>
    <country name="Panama">
        <rank updated="yes">69</rank>
        <year>2011</year>
        <gdppc>13600</gdppc>
        <neighbor name="Costa Rica" direction="W"/>
        <neighbor name="Colombia" direction="E"/>
    </country>
</data>

xml数据

在xml协议中各个语言都是支持的，在python中可以用以下模块操作xml；

print(root.iter(‘year‘)) #全文搜索
 print(root.find(‘country‘)) #在root的子节点找，只找一个
 print(root.findall(‘country‘)) #在root的子节点找，找所有

import xml.etree.ElementTree as ET
tree = ET.parse("xmltest.xml")
root = tree.getroot()
print(root.tag)
以上是固定格式

遍历xml文档

for child in root:
    print(‘========>‘,child.tag,child.attrib,child.attrib[‘name‘])
    for i in child:
        print(i.tag,i.attrib,i.text) 

只遍历year 节点

for node in root.iter(‘year‘):
    print(node.tag,node.text)
#---------------------------------------

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‘)
    node.set(‘version‘,‘1.0‘)
tree.write(‘test.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‘)

自己创建xml文档

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 = ‘33‘
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