XML模块

XML

XML:

• 客户端向服务器发送请求，服务器返回的都是字符串。
• 字符串可以是html模式，可以是字典形式(json模式)，也可以是xml模式。
• xml模块专门处理xml模式的字符串。
• xml本质是实现不同语言或程序之间进行数据交换的协议。

XML文件格式如下：

 1 <data>
 2     <country name="Liechtenstein">
 3         <rank updated="yes">2</rank>
 4         <year>2023</year>
 5         <gdppc>141100</gdppc>
 6         <neighbor direction="E" name="Austria" />
 7         <neighbor direction="W" name="Switzerland" />
 8     </country>
 9     <country name="Singapore">
10         <rank updated="yes">5</rank>
11         <year>2026</year>
12         <gdppc>59900</gdppc>
13         <neighbor direction="N" name="Malaysia" />
14     </country>
15     <country name="Panama">
16         <rank updated="yes">69</rank>
17         <year>2026</year>
18         <gdppc>13600</gdppc>
19         <neighbor direction="W" name="Costa Rica" />
20         <neighbor direction="E" name="Colombia" />
21     </country>
22 </data>
23
24 xml格式代码

xml格式代码

1、解析XML

1 from xml.etree import ElementTree as ET
2
3
4 # 打开文件，读取XML内容
5 str_xml = open(‘xo.xml‘, ‘r‘).read()
6
7 # 将字符串解析成xml特殊对象，root代指xml文件的根节点
8 root = ET.XML(str_xml)

利用ElementTree.XML将字符串解析成xml对象

 1 from xml.etree import ElementTree as ET
 2
 3 # 直接解析xml文件
 4 tree = ET.parse("xo.xml")
 5 ‘‘‘
 6 一切对象
 7 对象都是由类创建，对象所有的功能都在与其相关的类中
 8 1.本质是ElementTree类创建的，等价于 tree = ET.ElementTree()
 9 2.getroot() 获取xml根节点
10 3.write() 内存中的xml写进文件
11 ‘‘‘
12
13 # 获取xml文件的根节点
14 root = tree.getroot()
15
16 利用ElementTree.parse将文件直接解析成xml对象

利用ElementTree.parse将文件直接解析成xml对象

 1 from xml.etree import ElementTree as ET
 2
 3 #从字符串中解析xml得到一个Element对象
 4 str_xml = open(‘first.xml‘, ‘r‘).read()
 5 root = ET.XML(str_xml)
 6
 7 #从Element对象转换成ElementTree对象，参数提供root
 8 #一个root代表一个树
 9 tree = Element(root)
10
11 从第一种解析方式转换到第二种

从第一种解析方式转换到第二种

2、2、操作XML（Element类的功能）

　　XML格式类型是节点嵌套节点，对于每一个节点均有以下功能，以便对当前节点进行操作：

  1 class Element:
  2     """An XML element.
  3
  4     This class is the reference implementation of the Element interface.
  5
  6     An element‘s length is its number of subelements.  That means if you
  7     want to check if an element is truly empty, you should check BOTH
  8     its length AND its text attribute.
  9
 10     The element tag, attribute names, and attribute values can be either
 11     bytes or strings.
 12
 13     *tag* is the element name.  *attrib* is an optional dictionary containing
 14     element attributes. *extra* are additional element attributes given as
 15     keyword arguments.
 16
 17     Example form:
 18         <tag attrib>text<child/>...</tag>tail
 19
 20     """
 21
 22     当前节点的标签名
 23     tag = None
 24     """The element‘s name."""
 25
 26     当前节点的属性
 27
 28     attrib = None
 29     """Dictionary of the element‘s attributes."""
 30
 31     当前节点的内容
 32     text = None
 33     """
 34     Text before first subelement. This is either a string or the value None.
 35     Note that if there is no text, this attribute may be either
 36     None or the empty string, depending on the parser.
 37
 38     """
 39
 40     tail = None
 41     """
 42     Text after this element‘s end tag, but before the next sibling element‘s
 43     start tag.  This is either a string or the value None.  Note that if there
 44     was no text, this attribute may be either None or an empty string,
 45     depending on the parser.
 46
 47     """
 48
 49     def __init__(self, tag, attrib={}, **extra):
 50         if not isinstance(attrib, dict):
 51             raise TypeError("attrib must be dict, not %s" % (
 52                 attrib.__class__.__name__,))
 53         attrib = attrib.copy()
 54         attrib.update(extra)
 55         self.tag = tag
 56         self.attrib = attrib
 57         self._children = []
 58
 59     def __repr__(self):
 60         return "<%s %r at %#x>" % (self.__class__.__name__, self.tag, id(self))
 61
 62     def makeelement(self, tag, attrib):
 63         创建一个新节点
 64         """Create a new element with the same type.
 65
 66         *tag* is a string containing the element name.
 67         *attrib* is a dictionary containing the element attributes.
 68
 69         Do not call this method, use the SubElement factory function instead.
 70
 71         """
 72         return self.__class__(tag, attrib)
 73
 74     def copy(self):
 75         """Return copy of current element.
 76
 77         This creates a shallow copy. Subelements will be shared with the
 78         original tree.
 79
 80         """
 81         elem = self.makeelement(self.tag, self.attrib)
 82         elem.text = self.text
 83         elem.tail = self.tail
 84         elem[:] = self
 85         return elem
 86
 87     def __len__(self):
 88         return len(self._children)
 89
 90     def __bool__(self):
 91         warnings.warn(
 92             "The behavior of this method will change in future versions.  "
 93             "Use specific ‘len(elem)‘ or ‘elem is not None‘ test instead.",
 94             FutureWarning, stacklevel=2
 95             )
 96         return len(self._children) != 0 # emulate old behaviour, for now
 97
 98     def __getitem__(self, index):
 99         return self._children[index]
100
101     def __setitem__(self, index, element):
102         # if isinstance(index, slice):
103         #     for elt in element:
104         #         assert iselement(elt)
105         # else:
106         #     assert iselement(element)
107         self._children[index] = element
108
109     def __delitem__(self, index):
110         del self._children[index]
111
112     def append(self, subelement):
113         为当前节点追加一个子节点
114         """Add *subelement* to the end of this element.
115
116         The new element will appear in document order after the last existing
117         subelement (or directly after the text, if it‘s the first subelement),
118         but before the end tag for this element.
119
120         """
121         self._assert_is_element(subelement)
122         self._children.append(subelement)
123
124     def extend(self, elements):
125         为当前节点扩展 n 个子节点
126         """Append subelements from a sequence.
127
128         *elements* is a sequence with zero or more elements.
129
130         """
131         for element in elements:
132             self._assert_is_element(element)
133         self._children.extend(elements)
134
135     def insert(self, index, subelement):
136         在当前节点的子节点中插入某个节点，即：为当前节点创建子节点，然后插入指定位置
137         """Insert *subelement* at position *index*."""
138         self._assert_is_element(subelement)
139         self._children.insert(index, subelement)
140
141     def _assert_is_element(self, e):
142         # Need to refer to the actual Python implementation, not the
143         # shadowing C implementation.
144         if not isinstance(e, _Element_Py):
145             raise TypeError(‘expected an Element, not %s‘ % type(e).__name__)
146
147     def remove(self, subelement):
148         在当前节点在子节点中删除某个节点
149         """Remove matching subelement.
150
151         Unlike the find methods, this method compares elements based on
152         identity, NOT ON tag value or contents.  To remove subelements by
153         other means, the easiest way is to use a list comprehension to
154         select what elements to keep, and then use slice assignment to update
155         the parent element.
156
157         ValueError is raised if a matching element could not be found.
158
159         """
160         # assert iselement(element)
161         self._children.remove(subelement)
162
163     def getchildren(self):
164         获取所有的子节点（废弃）
165         """(Deprecated) Return all subelements.
166
167         Elements are returned in document order.
168
169         """
170         warnings.warn(
171             "This method will be removed in future versions.  "
172             "Use ‘list(elem)‘ or iteration over elem instead.",
173             DeprecationWarning, stacklevel=2
174             )
175         return self._children
176
177     def find(self, path, namespaces=None):
178         获取第一个寻找到的子节点
179         """Find first matching element by tag name or path.
180
181         *path* is a string having either an element tag or an XPath,
182         *namespaces* is an optional mapping from namespace prefix to full name.
183
184         Return the first matching element, or None if no element was found.
185
186         """
187         return ElementPath.find(self, path, namespaces)
188
189     def findtext(self, path, default=None, namespaces=None):
190         获取第一个寻找到的子节点的内容
191         """Find text for first matching element by tag name or path.
192
193         *path* is a string having either an element tag or an XPath,
194         *default* is the value to return if the element was not found,
195         *namespaces* is an optional mapping from namespace prefix to full name.
196
197         Return text content of first matching element, or default value if
198         none was found.  Note that if an element is found having no text
199         content, the empty string is returned.
200
201         """
202         return ElementPath.findtext(self, path, default, namespaces)
203
204     def findall(self, path, namespaces=None):
205         获取所有的子节点
206         """Find all matching subelements by tag name or path.
207
208         *path* is a string having either an element tag or an XPath,
209         *namespaces* is an optional mapping from namespace prefix to full name.
210
211         Returns list containing all matching elements in document order.
212
213         """
214         return ElementPath.findall(self, path, namespaces)
215
216     def iterfind(self, path, namespaces=None):
217         获取所有指定的节点，并创建一个迭代器（可以被for循环）
218         """Find all matching subelements by tag name or path.
219
220         *path* is a string having either an element tag or an XPath,
221         *namespaces* is an optional mapping from namespace prefix to full name.
222
223         Return an iterable yielding all matching elements in document order.
224
225         """
226         return ElementPath.iterfind(self, path, namespaces)
227
228     def clear(self):
229         清空节点
230         """Reset element.
231
232         This function removes all subelements, clears all attributes, and sets
233         the text and tail attributes to None.
234
235         """
236         self.attrib.clear()
237         self._children = []
238         self.text = self.tail = None
239
240     def get(self, key, default=None):
241         获取当前节点的属性值
242         """Get element attribute.
243
244         Equivalent to attrib.get, but some implementations may handle this a
245         bit more efficiently.  *key* is what attribute to look for, and
246         *default* is what to return if the attribute was not found.
247
248         Returns a string containing the attribute value, or the default if
249         attribute was not found.
250
251         """
252         return self.attrib.get(key, default)
253
254     def set(self, key, value):
255         为当前节点设置属性值
256         """Set element attribute.
257
258         Equivalent to attrib[key] = value, but some implementations may handle
259         this a bit more efficiently.  *key* is what attribute to set, and
260         *value* is the attribute value to set it to.
261
262         """
263         self.attrib[key] = value
264
265     def keys(self):
266         获取当前节点的所有属性的 key
267
268         """Get list of attribute names.
269
270         Names are returned in an arbitrary order, just like an ordinary
271         Python dict.  Equivalent to attrib.keys()
272
273         """
274         return self.attrib.keys()
275
276     def items(self):
277         获取当前节点的所有属性值，每个属性都是一个键值对
278         """Get element attributes as a sequence.
279
280         The attributes are returned in arbitrary order.  Equivalent to
281         attrib.items().
282
283         Return a list of (name, value) tuples.
284
285         """
286         return self.attrib.items()
287
288     def iter(self, tag=None):
289         在当前节点的子孙中根据节点名称寻找所有指定的节点，并返回一个迭代器（可以被for循环）。
290         """Create tree iterator.
291
292         The iterator loops over the element and all subelements in document
293         order, returning all elements with a matching tag.
294
295         If the tree structure is modified during iteration, new or removed
296         elements may or may not be included.  To get a stable set, use the
297         list() function on the iterator, and loop over the resulting list.
298
299         *tag* is what tags to look for (default is to return all elements)
300
301         Return an iterator containing all the matching elements.
302
303         """
304         if tag == "*":
305             tag = None
306         if tag is None or self.tag == tag:
307             yield self
308         for e in self._children:
309             yield from e.iter(tag)
310
311     # compatibility
312     def getiterator(self, tag=None):
313         # Change for a DeprecationWarning in 1.4
314         warnings.warn(
315             "This method will be removed in future versions.  "
316             "Use ‘elem.iter()‘ or ‘list(elem.iter())‘ instead.",
317             PendingDeprecationWarning, stacklevel=2
318         )
319         return list(self.iter(tag))
320
321     def itertext(self):
322         在当前节点的子孙中根据节点名称寻找所有指定的节点的内容，并返回一个迭代器（可以被for循环）。
323         """Create text iterator.
324
325         The iterator loops over the element and all subelements in document
326         order, returning all inner text.
327
328         """
329         tag = self.tag
330         if not isinstance(tag, str) and tag is not None:
331             return
332         if self.text:
333             yield self.text
334         for e in self:
335             yield from e.itertext()
336             if e.tail:
337                 yield e.tail
338
339 Element类

Element类

　　由于 每个节点 都具有以上的方法，并且在上一步骤中解析时均得到了root（xml文件的根节点），可以利用以上方法进行操作xml文件。

　　a、遍历XML文档的所有内容

 1 from xml.etree import ElementTree as ET
 2
 3 ############ 解析方式一 ############
 4 """
 5 # 打开文件，读取XML内容
 6 str_xml = open(‘xo.xml‘, ‘r‘).read()
 7
 8 # 将字符串解析成xml特殊对象，root代指xml文件的根节点
 9 root = ET.XML(str_xml)
10 """
11 ############ 解析方式二 ############
12
13 # 直接解析xml文件
14 tree = ET.parse("xo.xml")
15
16 # 获取xml文件的根节点
17 root = tree.getroot()
18
19
20 ### 操作
21
22 # 顶层标签
23 print(root.tag)
24
25
26 # 遍历XML文档的第二层
27 for child in root:
28     # 第二层节点的标签名称和标签属性
29     print(child.tag, child.attrib)
30     # 遍历XML文档的第三层
31     for i in child:
32         # 第二层节点的标签名称和内容
33         print(i.tag,i.text)
34
35 遍历xml所有内容

遍历xml所有内容

　　b、遍历XML中指定的节点

 1 from xml.etree import ElementTree as ET
 2
 3 ############ 解析方式一 ############
 4 """
 5 # 打开文件，读取XML内容
 6 str_xml = open(‘xo.xml‘, ‘r‘).read()
 7
 8 # 将字符串解析成xml特殊对象，root代指xml文件的根节点
 9 root = ET.XML(str_xml)
10 """
11 ############ 解析方式二 ############
12
13 # 直接解析xml文件
14 tree = ET.parse("xo.xml")
15
16 # 获取xml文件的根节点
17 root = tree.getroot()
18
19
20 ### 操作
21
22 # 顶层标签
23 print(root.tag)
24
25
26 # 遍历XML中所有的year节点
27 for node in root.iter(‘year‘):
28     # 节点的标签名称和内容
29     print(node.tag, node.text)
30
31 遍历xml指定节点

遍历xml指定节点

　　c、修改节点内容

　　由于修改的节点时，均是在内存中进行，其不会影响文件中的内容。所以，如果想要修改，则需要重新将内存中的内容写到文件。

　　1.解析字符串方式，修改，保存

 1 from xml.etree import ElementTree as ET
 2
 3 ############ 解析方式一 ############
 4
 5 # 打开文件，读取XML内容
 6 str_xml = open(‘xo.xml‘, ‘r‘).read()
 7
 8 # 将字符串解析成xml特殊对象，root代指xml文件的根节点
 9 root = ET.XML(str_xml)
10
11 ############ 操作 ############
12
13 # 顶层标签
14 print(root.tag)
15
16 # 循环所有的year节点
17 for node in root.iter(‘year‘):
18     # 将year节点中的内容自增一
19     new_year = int(node.text) + 1
20     node.text = str(new_year)
21
22     # 设置属性
23     node.set(‘name‘, ‘alex‘)
24     node.set(‘age‘, ‘18‘)
25     # 删除属性
26     del node.attrib[‘name‘]
27
28
29 ############ 保存文件 ############
30 tree = ET.ElementTree(root)
31 tree.write("newnew.xml", encoding=‘utf-8‘)
32
33 法1

法1

　　2.解析文件方式，修改，保存

 1 from xml.etree import ElementTree as ET
 2
 3 ############ 解析方式二 ############
 4
 5 # 直接解析xml文件
 6 tree = ET.parse("xo.xml")
 7
 8 # 获取xml文件的根节点
 9 root = tree.getroot()
10
11 ############ 操作 ############
12
13 # 顶层标签
14 print(root.tag)
15
16 # 循环所有的year节点
17 for node in root.iter(‘year‘):
18     # 将year节点中的内容自增一
19     new_year = int(node.text) + 1
20     node.text = str(new_year)
21
22     # 设置属性
23     node.set(‘name‘, ‘alex‘)
24     node.set(‘age‘, ‘18‘)
25     # 删除属性
26     del node.attrib[‘name‘]
27
28
29 ############ 保存文件 ############
30 tree.write("newnew.xml", encoding=‘utf-8‘)
31
32 法2

法2

　　d、删除节点

　　1.解析字符串方式打开，删除，保存

 1 from xml.etree import ElementTree as ET
 2
 3 ############ 解析字符串方式打开 ############
 4
 5 # 打开文件，读取XML内容
 6 str_xml = open(‘xo.xml‘, ‘r‘).read()
 7
 8 # 将字符串解析成xml特殊对象，root代指xml文件的根节点
 9 root = ET.XML(str_xml)
10
11 ############ 操作 ############
12
13 # 顶层标签
14 print(root.tag)
15
16 # 遍历data下的所有country节点
17 for country in root.findall(‘country‘):
18     # 获取每一个country节点下rank节点的内容
19     rank = int(country.find(‘rank‘).text)
20
21     if rank > 50:
22         # 删除指定country节点
23         root.remove(country)
24
25 ############ 保存文件 ############
26 tree = ET.ElementTree(root)
27 tree.write("newnew.xml", encoding=‘utf-8‘)
28
29 法1

法1

　　2.解析文件方式打开，删除，保存

 1 from xml.etree import ElementTree as ET
 2
 3 ############ 解析文件方式 ############
 4
 5 # 直接解析xml文件
 6 tree = ET.parse("xo.xml")
 7
 8 # 获取xml文件的根节点
 9 root = tree.getroot()
10
11 ############ 操作 ############
12
13 # 顶层标签
14 print(root.tag)
15
16 # 遍历data下的所有country节点
17 for country in root.findall(‘country‘):
18     # 获取每一个country节点下rank节点的内容
19     rank = int(country.find(‘rank‘).text)
20
21     if rank > 50:
22         # 删除指定country节点
23         root.remove(country)
24
25 ############ 保存文件 ############
26 tree.write("newnew.xml", encoding=‘utf-8‘)
27
28 法2

法2

3、创建XML文档

　　1.创建方式（一）

 1 from xml.etree import ElementTree as ET
 2
 3
 4 # 创建根节点
 5 root = ET.Element("famliy")
 6
 7
 8 # 创建节点大儿子
 9 son1 = ET.Element(‘son‘, {‘name‘: ‘儿1‘})
10 # 创建小儿子
11 son2 = ET.Element(‘son‘, {"name": ‘儿2‘})
12
13 # 在大儿子中创建两个孙子
14 grandson1 = ET.Element(‘grandson‘, {‘name‘: ‘儿11‘})
15 grandson2 = ET.Element(‘grandson‘, {‘name‘: ‘儿12‘})
16 son1.append(grandson1)
17 son1.append(grandson2)
18
19
20 # 把儿子添加到根节点中
21 root.append(son1)
22 root.append(son1)
23
24 tree = ET.ElementTree(root)
25 tree.write(‘oooo.xml‘,encoding=‘utf-8‘, short_empty_elements=False)
26
27 手动创建：ET.Element

手动创建：ET.Element

　　2.创建方式（二）

 1 from xml.etree import ElementTree as ET
 2
 3 # 创建根节点
 4 root = ET.Element("famliy")
 5
 6
 7 # 创建大儿子
 8 # son1 = ET.Element(‘son‘, {‘name‘: ‘儿1‘})
 9 son1 = root.makeelement(‘son‘, {‘name‘: ‘儿1‘})
10 # 创建小儿子
11 # son2 = ET.Element(‘son‘, {"name": ‘儿2‘})
12 son2 = root.makeelement(‘son‘, {"name": ‘儿2‘})
13
14 # 在大儿子中创建两个孙子
15 # grandson1 = ET.Element(‘grandson‘, {‘name‘: ‘儿11‘})
16 grandson1 = son1.makeelement(‘grandson‘, {‘name‘: ‘儿11‘})
17 # grandson2 = ET.Element(‘grandson‘, {‘name‘: ‘儿12‘})
18 grandson2 = son1.makeelement(‘grandson‘, {‘name‘: ‘儿12‘})
19
20 son1.append(grandson1)
21 son1.append(grandson2)
22
23
24 # 把儿子添加到根节点中
25 root.append(son1)
26 root.append(son1)
27
28 tree = ET.ElementTree(root)
29 tree.write(‘oooo.xml‘,encoding=‘utf-8‘, short_empty_elements=False)
30
31 用someNode.makeelement创建

用someNode.makeelement创建

　　3.创建方式（三）

 1 from xml.etree import ElementTree as ET
 2
 3
 4 # 创建根节点
 5 root = ET.Element("famliy")
 6
 7
 8 # 创建节点大儿子
 9 son1 = ET.SubElement(root, "son", attrib={‘name‘: ‘儿1‘})
10 # 创建小儿子
11 son2 = ET.SubElement(root, "son", attrib={"name": "儿2"})
12
13 # 在大儿子中创建一个孙子
14 grandson1 = ET.SubElement(son1, "age", attrib={‘name‘: ‘儿11‘})
15 grandson1.text = ‘孙子‘
16
17
18 et = ET.ElementTree(root)  #生成文档对象
19 et.write("test.xml", encoding="utf-8", xml_declaration=True, short_empty_elements=False)
20
21 ET.subElement创建并append

ET.subElement创建并append

　　4.由于原生保存的XML时默认无缩进，如果想要设置缩进的话， 需要修改保存方式：

 1 from xml.etree import ElementTree as ET
 2 from xml.dom import minidom
 3
 4
 5 def prettify(elem):
 6     """将节点转换成字符串，并添加缩进。
 7     """
 8     rough_string = ET.tostring(elem, ‘utf-8‘)
 9     reparsed = minidom.parseString(rough_string)
10     return reparsed.toprettyxml(indent="\t")
11
12 # 创建根节点
13 root = ET.Element("famliy")
14
15
16 # 创建大儿子
17 # son1 = ET.Element(‘son‘, {‘name‘: ‘儿1‘})
18 son1 = root.makeelement(‘son‘, {‘name‘: ‘儿1‘})
19 # 创建小儿子
20 # son2 = ET.Element(‘son‘, {"name": ‘儿2‘})
21 son2 = root.makeelement(‘son‘, {"name": ‘儿2‘})
22
23 # 在大儿子中创建两个孙子
24 # grandson1 = ET.Element(‘grandson‘, {‘name‘: ‘儿11‘})
25 grandson1 = son1.makeelement(‘grandson‘, {‘name‘: ‘儿11‘})
26 # grandson2 = ET.Element(‘grandson‘, {‘name‘: ‘儿12‘})
27 grandson2 = son1.makeelement(‘grandson‘, {‘name‘: ‘儿12‘})
28
29 son1.append(grandson1)
30 son1.append(grandson2)
31
32
33 # 把儿子添加到根节点中
34 root.append(son1)
35 root.append(son1)
36
37
38 raw_str = prettify(root)
39
40 f = open("xxxoo.xml",‘w‘,encoding=‘utf-8‘)
41 f.write(raw_str)
42 f.close()
43
44 法4

法4