Python之xml文件处理（一）——使用ElementTree遍历xml

发现python上有关xml的实现方法还是蛮多的，第三方的框架也不少，但是其中没有像dom4j那样名声响亮的框架。所以，还是中规中居地介绍python的故有方法吧。

今天，先介绍一个ElementTree，看着还顺眼些。详细说明在代码注释中，结果在后面。

1#coding:utf-8
2'''
3Created on 2015年1月12日
4
5@author: neil
6'''
7from xml.etree import ElementTree
8
9#xml内容以文件形式传入
10#filepath=''
11# with open(filepath,'rt') as f:
12#     tree=ElementTree.parse(f)
13
14#xml内容以字符串形式传入
15tree=ElementTree.fromstring('''<?xml version="1.0" encoding="utf-8"?>
16<catalog>
17       <maxid id='0'>4</maxid>尾巴
18       <login id='1' username="pytest" passwd='123456'>
19            　　<caption>Python</caption>
20             <item id="4">
21                    <caption>测试</caption>
22            </item>
23    </login>
24    <item id="2">
25            <caption>Zope</caption>
26            <caption>JJJ</caption>
27    </item>
28<mux>sdfsdfsdfs</mux>
29</catalog>''')
30
31for node in tree.iter():#深度搜索、树的先序遍历
32    print type(node)
33    print 'tag:',node.tag#元素标签名
34    print 'tail:',node.tail#</XXX>后面的字符串，多半是回车换行。根结点的结束标签后面文档结束，所以是None。
35    print 'attrib:',node.attrib#字典类型，字典的项对应元素属性，字典的键对应属性名称，字典的值对应属性值
36    print 'attrib-id-default:',node.attrib.get('id','NULL')#字典方法，按键取值，如果键不存在，就取默认值。默认值由第二个参数规定。
37    print 'attrib-id:',node.attrib.get('id')#字典方法，按键取值，如果键不存在，就取None,不会报错。
38    print 'attrib.items:',node.attrib.items()#二元元组的列表，列表的每一个项是一个二元元组，元组的前一个值是xml元素属性的名称，后一个值是属性的值。
39    print 'attrib.keys:',node.attrib.keys()#以列表的形式列举元素的所有属性名称
40    print 'find-caption:',node.find('caption')#只在该结点的所有子节点中选择符合元素名称的第一个子节点
41    print 'find-item:',node.find('item')
42    print 'findall:',node.findall('caption')#只在该结点的所有子节点中选择符合元素名称的所有子节点，范围类型为列表
43    print 'findtext-caption:',node.findtext('caption')#只在该结点的所有子节点中选择符合元素内容的第一个子节点
44    print 'getchildren:',node.getchildren() #所有子节点以列表形式给出
45    print 'iter:',node.iter()
46    for n in node.iter():#深度搜索、树的先序遍历该结点下的子树
47        print '++++',n.tag
48    print '- - - - - - - - - - - - - - - - '

输出结果如下：

1<class 'xml.etree.ElementTree.Element'>
2tag: catalog
3tail: None
4attrib: {}
5attrib-id-default: NULL
6attrib-id: None
7attrib.items: []
8attrib.keys: []
9find-caption: None
10find-item: <Element 'item' at 0x7f738e1f1c10>
11findall: []
12findtext-caption: None
13getchildren: [<Element 'maxid' at 0x7f738e1f1850>, <Element 'login' at 0x7f738e1f1890>, <Element 'item' at 0x7f738e1f1c10>, <Element 'mux' at 0x7f738e1f1cd0>]
14iter: <generator object iter at 0x7f738e1e72d0>
15++++ catalog
16++++ maxid
17++++ login
18++++ caption
19++++ item
20++++ caption
21++++ item
22++++ caption
23++++ caption
24++++ mux
25- - - - - - - - - - - - - - - - 
26<class 'xml.etree.ElementTree.Element'>
27tag: maxid
28tail: 尾巴
29       
30attrib: {'id': '0'}
31attrib-id-default: 0
32attrib-id: 0
33attrib.items: [('id', '0')]
34attrib.keys: ['id']
35find-caption: None
36find-item: None
37findall: []
38findtext-caption: None
39getchildren: []
40iter: <generator object iter at 0x7f738e1e7370>
41++++ maxid
42- - - - - - - - - - - - - - - - 
43<class 'xml.etree.ElementTree.Element'>
44tag: login
45tail: 
46    
47attrib: {'username': 'pytest', 'passwd': '123456', 'id': '1'}
48attrib-id-default: 1
49attrib-id: 1
50attrib.items: [('username', 'pytest'), ('passwd', '123456'), ('id', '1')]
51attrib.keys: ['username', 'passwd', 'id']
52find-caption: <Element 'caption' at 0x7f738e1f1950>
53find-item: <Element 'item' at 0x7f738e1f1a10>
54findall: [<Element 'caption' at 0x7f738e1f1950>]
55findtext-caption: Python
56getchildren: [<Element 'caption' at 0x7f738e1f1950>, <Element 'item' at 0x7f738e1f1a10>]
57iter: <generator object iter at 0x7f738e1e7370>
58++++ login
59++++ caption
60++++ item
61++++ caption
62- - - - - - - - - - - - - - - - 
63<class 'xml.etree.ElementTree.Element'>
64tag: caption
65tail: 
66             
67attrib: {}
68attrib-id-default: NULL
69attrib-id: None
70attrib.items: []
71attrib.keys: []
72find-caption: None
73find-item: None
74findall: []
75findtext-caption: None
76getchildren: []
77iter: <generator object iter at 0x7f738e1e73c0>
78++++ caption
79- - - - - - - - - - - - - - - - 
80<class 'xml.etree.ElementTree.Element'>
81tag: item
82tail: 
83    
84attrib: {'id': '4'}
85attrib-id-default: 4
86attrib-id: 4
87attrib.items: [('id', '4')]
88attrib.keys: ['id']
89find-caption: <Element 'caption' at 0x7f738e1f1bd0>
90find-item: None
91findall: [<Element 'caption' at 0x7f738e1f1bd0>]
92findtext-caption: 测试
93getchildren: [<Element 'caption' at 0x7f738e1f1bd0>]
94iter: <generator object iter at 0x7f738e1e73c0>
95++++ item
96++++ caption
97- - - - - - - - - - - - - - - - 
98<class 'xml.etree.ElementTree.Element'>
99tag: caption
100tail: 
101            
102attrib: {}
103attrib-id-default: NULL
104attrib-id: None
105attrib.items: []
106attrib.keys: []
107find-caption: None
108find-item: None
109findall: []
110findtext-caption: None
111getchildren: []
112iter: <generator object iter at 0x7f738e1e7410>
113++++ caption
114- - - - - - - - - - - - - - - - 
115<class 'xml.etree.ElementTree.Element'>
116tag: item
117tail: 
118
119attrib: {'id': '2'}
120attrib-id-default: 2
121attrib-id: 2
122attrib.items: [('id', '2')]
123attrib.keys: ['id']
124find-caption: <Element 'caption' at 0x7f738e1f1c50>
125find-item: None
126findall: [<Element 'caption' at 0x7f738e1f1c50>, <Element 'caption' at 0x7f738e1f1c90>]
127findtext-caption: Zope
128getchildren: [<Element 'caption' at 0x7f738e1f1c50>, <Element 'caption' at 0x7f738e1f1c90>]
129iter: <generator object iter at 0x7f738e1e7370>
130++++ item
131++++ caption
132++++ caption
133- - - - - - - - - - - - - - - - 
134<class 'xml.etree.ElementTree.Element'>
135tag: caption
136tail: 
137            
138attrib: {}
139attrib-id-default: NULL
140attrib-id: None
141attrib.items: []
142attrib.keys: []
143find-caption: None
144find-item: None
145findall: []
146findtext-caption: None
147getchildren: []
148iter: <generator object iter at 0x7f738e1e73c0>
149++++ caption
150- - - - - - - - - - - - - - - - 
151<class 'xml.etree.ElementTree.Element'>
152tag: caption
153tail: 
154    
155attrib: {}
156attrib-id-default: NULL
157attrib-id: None
158attrib.items: []
159attrib.keys: []
160find-caption: None
161find-item: None
162findall: []
163findtext-caption: None
164getchildren: []
165iter: <generator object iter at 0x7f738e1e73c0>
166++++ caption
167- - - - - - - - - - - - - - - - 
168<class 'xml.etree.ElementTree.Element'>
169tag: mux
170tail: 
171
172attrib: {}
173attrib-id-default: NULL
174attrib-id: None
175attrib.items: []
176attrib.keys: []
177find-caption: None
178find-item: None
179findall: []
180findtext-caption: None
181getchildren: []
182iter: <generator object iter at 0x7f738e1e7370>
183++++ mux
184- - - - - - - - - - - - - - - -

Element具有的属性和方法：

• tag

• A string identifying what kind of data this element represents (the element type, in other words).

• text

• The text attribute can be used to hold additional data associated with the element. As the name implies this attribute is usually a string but may be any application-specific object. If the element is created from an XML file the attribute will contain any text found between the element tags.

• tail

• The tail attribute can be used to hold additional data associated with the element. This attribute is usually a string but may be any application-specific object. If the element is created from an XML file the attribute will contain any text found after the element’s end tag and before the next tag.

• attrib

• A dictionary containing the element’s attributes. Note that while the attrib value is always a real mutable Python dictionary, an ElementTree implementation may choose to use another internal representation, and create the dictionary only if someone asks for it. To take advantage of such implementations, use the dictionary methods below whenever possible.

The following dictionary-like methods work on the element attributes.

• clear()

• Resets an element. This function removes all subelements, clears all attributes, and sets the text and tail attributes to None.

• get(key,default=None)

• Gets the element attribute named key.

  Returns the attribute value, or default if the attribute was not found.

• items()

• Returns the element attributes as a sequence of (name, value) pairs. The attributes are returned in an arbitrary order.

• keys()

• Returns the elements attribute names as a list. The names are returned in an arbitrary order.

• set(key,value)

• Set the attribute key on the element to value.

The following methods work on the element’s children (subelements).

• append(subelement)

• Adds the element subelement to the end of this elements internal list of subelements.

• extend(subelements)

• Appends subelements from a sequence object with zero or more elements. RaisesAssertionError if a subelement is not a valid object.

  New in version 2.7.

• find(match)

• Finds the first subelement matching match. match may be a tag name or path. Returns an element instance orNone.

• findall(match)

• Finds all matching subelements, by tag name or path. Returns a list containing all matching elements in document order.

• findtext(match,default=None)

• Finds text for the first subelement matching match. match may be a tag name or path. Returns the text content of the first matching element, or_default_ if no element was found. Note that if the matching element has no text content an empty string is returned.

• getchildren()

• Deprecated since version 2.7:Uselist(elem) or iteration.

• getiterator(tag=None)

• Deprecated since version 2.7:Use method Element.iter() instead.

• insert(index,element)

• Inserts a subelement at the given position in this element.

• iter(tag=None)

• Creates a tree iterator with the current element as the root. The iterator iterates over this element and all elements below it, in document (depth first) order. If tag is not None or '*', only elements whose tag equals tag are returned from the iterator. If the tree structure is modified during iteration, the result is undefined.

• iterfind(match)

• Finds all matching subelements, by tag name or path. Returns an iterable yielding all matching elements in document order.

  New in version 2.7.

• itertext()

• Creates a text iterator. The iterator loops over this element and all subelements, in document order, and returns all inner text.

  New in version 2.7.

• makeelement(tag,attrib)

• Creates a new element object of the same type as this element. Do not call this method, use the SubElement() factory function instead.

• remove(subelement)

• Removes subelement from the element. Unlike the find* methods this method compares elements based on the instance identity, not on tag value or contents.

ElementTree具有的属性和方法：

• _setroot(element)

• Replaces the root element for this tree. This discards the current contents of the tree, and replaces it with the given element. Use with care.element is an element instance.

• find(match)

• Finds the first toplevel element matching match. match may be a tag name or path. Same as getroot().find(match). Returns the first matching element, orNone if no element was found.

• findall(match)

• Finds all matching subelements, by tag name or path. Same as getroot().findall(match).match may be a tag name or path. Returns a list containing all matching elements, in document order.

• findtext(match,default=None)

• Finds the element text for the first toplevel element with given tag. Same as getroot().findtext(match).match may be a tag name or path.default is the value to return if the element was not found. Returns the text content of the first matching element, or the default value no element was found. Note that if the element is found, but has no text content, this method returns an empty string.

• getiterator(tag=None)

• Deprecated since version 2.7:Use method ElementTree.iter() instead.

• getroot()

• Returns the root element for this tree.

• iter(tag=None)

• Creates and returns a tree iterator for the root element. The iterator loops over all elements in this tree, in section order.tag is the tag to look for (default is to return all elements)

• iterfind(match)

• Finds all matching subelements, by tag name or path. Same as getroot().iterfind(match). Returns an iterable yielding all matching elements in document order.

  New in version 2.7.

• parse(source,parser=None)

• Loads an external XML section into this element tree. source is a file name or file object.parser is an optional parser instance. If not given, the standard XMLParser parser is used. Returns the section root element.

• write(file,encoding="us-ascii",xml_declaration=None,method="xml")

• Writes the element tree to a file, as XML. file is a file name, or a file object opened for writing.encoding[1] is the output encoding (default is US-ASCII).xml_declaration controls if an XML declaration should be added to the file. Use False for never, True for always, None for only if not US-ASCII or UTF-8 (default is None).method is either"xml","html" or"text" (default is"xml"). Returns an encoded string.