shevle模块比pickle模块简单，只要一个open模式，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
如下例题：
import shelve
# dic1={'pwd':'alex3714','age':18,'sex':'male'}
# dic2={'pwd':'alex3715','age':73,'sex':'male'}
d=shelve.open('db.txt',writeback=True)
d['egon']=dic1
d['alex']=dic2
d['egon']['age']=19
print(d['egon'])
d.close()
xml是实现不同语言或程序之间进行数据交换的协议，跟json差不多，单json使用起来更简单
<?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
import xml.etree.ElementTree as ET
tree = ET.parse("a.xml") #解析文件
root = tree.getroot() #树形结构，拿到树根
对于任何标签都有三个特征：标签名、标签属性、标签的文本内容
# print(root.tag) #标签
# print(root.attrib) #标签属性
# print(root.text) #标签的文本内容
全文搜索,找到所有
# for year in root.iter('year'):
# print(year.tag)
# print(year.attrib)
# print(year.text)
# print('='*100)
# print(root.find('country').attrib) #在root的子节点找，只找一个
# print([country.attrib for country in root.findall('country')]) #在root的子节点找，找所有
1、查
#遍历整个文档
# for country in root:
# print('============>国家 %s' %country.attrib)
# for item in country:
# print(item.tag)
# print(item.attrib)
# print(item.text)
2、改
# for year in root.iter('year'):
# print(year.tag)
# year.attrib={'updated':'yes'}
# year.text=str(int(year.text)+1)
#
# tree.write('a.xml')
3、增
# for country in root:
# rank=country.find('rank')
# if int(rank.text) > 50:
# # print('符号条的国家',country.attrib)
# tag=ET.Element('egon')
# tag.attrib={'updated':'yes'}
# tag.text='NB'
# country.append(tag)
#
# tree.write('a.xml')
4、删
for country in root:
tag=country.find('egon')
# print(tag,bool(tag))
if tag is not None:
print('====>')
country.remove(tag)
tree.write('a.xml')