python3 xml模块

缺乏、安全感 2022-01-07 23:47 384阅读 0赞

### 一.简介 ###

xml是实现不通语言或程序之间进行数据交换的协议，可扩展标记语言，标准通用标记语言的子集。是一种用于标记电子文件使其具有结构性的标记语言。xml格式如下，是通过<>节点来区别数据结构的。

**XML文件示例：**

<?xml version="1.0"?>
    <data>  # data 是根节点 <>开头<>结尾就表示为一个节点
        <country name="Liechtenstein">    # country节点,name是节点的属性，属性可以有多个，属性值必须用引号
            <rank updated="yes">2</rank>  # rank节点，updated是节点的属性，2表示文本内容
            <year>2023</year>
            <gdppc>141100</gdppc>
            <neighbor direction="E" name="Austria" />
            <neighbor direction="W" name="Switzerland" />
        </country>
        <country name="Singapore">
            <rank updated="yes">5</rank>
            <year>2026</year>
            <gdppc>59900</gdppc>
            <neighbor direction="N" name="Malaysia" />
        </country>
        <country name="Panama">
            <rank updated="yes">69</rank>
            <year>2026</year>
            <gdppc>13600</gdppc>
            <neighbor direction="W" name="Costa Rica" />
            <neighbor direction="E" name="Colombia" />
        </country>
    </data>

### 二.XML文件处理 ###

XML文件解析的两种方式：

1.  解析字符串方式
2.  解析文件方式

a.解析字符串方式
    # 加载模块，设置一个别名
    from xml.etree import ElementTree as ET
     
    # 打开文件，读取XML内容，print(str_xml)则获得整个xml文件中的内容，str_xml是个字符串
    str_xml = open('xo.xml', 'r').read()
     
     
    # 将字符串解析成xml特殊对象，root代指xml文件的根节点，print(root)将获取根节点的内存地址，print(root.tag)可以获取根节点的名称
    root = ET.XML(str_xml)
     
    b.解析文件方式
    from xml.etree import ElementTree as ET
     
    # 直接解析xml文件
    tree = ET.parse("xo.xml")
     
    # 获取xml文件的根节点
    root = tree.getroot()

**2.XML文件操作**

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

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][]

class Element:
        """An XML element.
     
        This class is the reference implementation of the Element interface.
     
        An element's length is its number of subelements.  That means if you
        want to check if an element is truly empty, you should check BOTH
        its length AND its text attribute.
     
        The element tag, attribute names, and attribute values can be either
        bytes or strings.
     
        *tag* is the element name.  *attrib* is an optional dictionary containing
        element attributes. *extra* are additional element attributes given as
        keyword arguments.
     
        Example form:
            <tag attrib>text<child/>...</tag>tail
     
        """
     
        当前节点的标签名
        tag = None
        """The element's name."""
     
        当前节点的属性
     
        attrib = None
        """Dictionary of the element's attributes."""
     
        当前节点的内容
        text = None
        """
        Text before first subelement. This is either a string or the value None.
        Note that if there is no text, this attribute may be either
        None or the empty string, depending on the parser.
     
        """
     
        tail = None
        """
        Text after this element's end tag, but before the next sibling element's
        start tag.  This is either a string or the value None.  Note that if there
        was no text, this attribute may be either None or an empty string,
        depending on the parser.
     
        """
     
        def __init__(self, tag, attrib={}, **extra):
            if not isinstance(attrib, dict):
                raise TypeError("attrib must be dict, not %s" % (
                    attrib.__class__.__name__,))
            attrib = attrib.copy()
            attrib.update(extra)
            self.tag = tag
            self.attrib = attrib
            self._children = []
     
        def __repr__(self):
            return "<%s %r at %#x>" % (self.__class__.__name__, self.tag, id(self))
     
        def makeelement(self, tag, attrib):
            创建一个新节点
            """Create a new element with the same type.
     
            *tag* is a string containing the element name.
            *attrib* is a dictionary containing the element attributes.
     
            Do not call this method, use the SubElement factory function instead.
     
            """
            return self.__class__(tag, attrib)
     
        def copy(self):
            """Return copy of current element.
     
            This creates a shallow copy. Subelements will be shared with the
            original tree.
     
            """
            elem = self.makeelement(self.tag, self.attrib)
            elem.text = self.text
            elem.tail = self.tail
            elem[:] = self
            return elem
     
        def __len__(self):
            return len(self._children)
     
        def __bool__(self):
            warnings.warn(
                "The behavior of this method will change in future versions.  "
                "Use specific 'len(elem)' or 'elem is not None' test instead.",
                FutureWarning, stacklevel=2
                )
            return len(self._children) != 0 # emulate old behaviour, for now
     
        def __getitem__(self, index):
            return self._children[index]
     
        def __setitem__(self, index, element):
            # if isinstance(index, slice):
            #     for elt in element:
            #         assert iselement(elt)
            # else:
            #     assert iselement(element)
            self._children[index] = element
     
        def __delitem__(self, index):
            del self._children[index]
     
        def append(self, subelement):
            为当前节点追加一个子节点
            """Add *subelement* to the end of this element.
     
            The new element will appear in document order after the last existing
            subelement (or directly after the text, if it's the first subelement),
            but before the end tag for this element.
     
            """
            self._assert_is_element(subelement)
            self._children.append(subelement)
     
        def extend(self, elements):
            为当前节点扩展 n 个子节点
            """Append subelements from a sequence.
     
            *elements* is a sequence with zero or more elements.
     
            """
            for element in elements:
                self._assert_is_element(element)
            self._children.extend(elements)
     
        def insert(self, index, subelement):
            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
            """Insert *subelement* at position *index*."""
            self._assert_is_element(subelement)
            self._children.insert(index, subelement)
     
        def _assert_is_element(self, e):
            # Need to refer to the actual Python implementation, not the
            # shadowing C implementation.
            if not isinstance(e, _Element_Py):
                raise TypeError('expected an Element, not %s' % type(e).__name__)
     
        def remove(self, subelement):
            在当前节点在子节点中删除某个节点
            """Remove matching subelement.
     
            Unlike the find methods, this method compares elements based on
            identity, NOT ON tag value or contents.  To remove subelements by
            other means, the easiest way is to use a list comprehension to
            select what elements to keep, and then use slice assignment to update
            the parent element.
     
            ValueError is raised if a matching element could not be found.
     
            """
            # assert iselement(element)
            self._children.remove(subelement)
     
        def getchildren(self):
            获取所有的子节点（废弃）
            """(Deprecated) Return all subelements.
     
            Elements are returned in document order.
     
            """
            warnings.warn(
                "This method will be removed in future versions.  "
                "Use 'list(elem)' or iteration over elem instead.",
                DeprecationWarning, stacklevel=2
                )
            return self._children
     
        def find(self, path, namespaces=None):
            获取第一个寻找到的子节点
            """Find first matching element by tag name or path.
     
            *path* is a string having either an element tag or an XPath,
            *namespaces* is an optional mapping from namespace prefix to full name.
     
            Return the first matching element, or None if no element was found.
     
            """
            return ElementPath.find(self, path, namespaces)
     
        def findtext(self, path, default=None, namespaces=None):
            获取第一个寻找到的子节点的内容
            """Find text for first matching element by tag name or path.
     
            *path* is a string having either an element tag or an XPath,
            *default* is the value to return if the element was not found,
            *namespaces* is an optional mapping from namespace prefix to full name.
     
            Return text content of first matching element, or default value if
            none was found.  Note that if an element is found having no text
            content, the empty string is returned.
     
            """
            return ElementPath.findtext(self, path, default, namespaces)
     
        def findall(self, path, namespaces=None):
            获取所有的子节点
            """Find all matching subelements by tag name or path.
     
            *path* is a string having either an element tag or an XPath,
            *namespaces* is an optional mapping from namespace prefix to full name.
     
            Returns list containing all matching elements in document order.
     
            """
            return ElementPath.findall(self, path, namespaces)
     
        def iterfind(self, path, namespaces=None):
            获取所有指定的节点，并创建一个迭代器（可以被for循环）
            """Find all matching subelements by tag name or path.
     
            *path* is a string having either an element tag or an XPath,
            *namespaces* is an optional mapping from namespace prefix to full name.
     
            Return an iterable yielding all matching elements in document order.
     
            """
            return ElementPath.iterfind(self, path, namespaces)
     
        def clear(self):
            清空节点
            """Reset element.
     
            This function removes all subelements, clears all attributes, and sets
            the text and tail attributes to None.
     
            """
            self.attrib.clear()
            self._children = []
            self.text = self.tail = None
     
        def get(self, key, default=None):
            获取当前节点的属性值
            """Get element attribute.
     
            Equivalent to attrib.get, but some implementations may handle this a
            bit more efficiently.  *key* is what attribute to look for, and
            *default* is what to return if the attribute was not found.
     
            Returns a string containing the attribute value, or the default if
            attribute was not found.
     
            """
            return self.attrib.get(key, default)
     
        def set(self, key, value):
            为当前节点设置属性值
            """Set element attribute.
     
            Equivalent to attrib[key] = value, but some implementations may handle
            this a bit more efficiently.  *key* is what attribute to set, and
            *value* is the attribute value to set it to.
     
            """
            self.attrib[key] = value
     
        def keys(self):
            获取当前节点的所有属性的 key
     
            """Get list of attribute names.
     
            Names are returned in an arbitrary order, just like an ordinary
            Python dict.  Equivalent to attrib.keys()
     
            """
            return self.attrib.keys()
     
        def items(self):
            获取当前节点的所有属性值，每个属性都是一个键值对
            """Get element attributes as a sequence.
     
            The attributes are returned in arbitrary order.  Equivalent to
            attrib.items().
     
            Return a list of (name, value) tuples.
     
            """
            return self.attrib.items()
     
        def iter(self, tag=None):
            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）。
            """Create tree iterator.
     
            The iterator loops over the element and all subelements in document
            order, returning all elements with a matching tag.
     
            If the tree structure is modified during iteration, new or removed
            elements may or may not be included.  To get a stable set, use the
            list() function on the iterator, and loop over the resulting list.
     
            *tag* is what tags to look for (default is to return all elements)
     
            Return an iterator containing all the matching elements.
     
            """
            if tag == "*":
                tag = None
            if tag is None or self.tag == tag:
                yield self
            for e in self._children:
                yield from e.iter(tag)
     
        # compatibility
        def getiterator(self, tag=None):
            # Change for a DeprecationWarning in 1.4
            warnings.warn(
                "This method will be removed in future versions.  "
                "Use 'elem.iter()' or 'list(elem.iter())' instead.",
                PendingDeprecationWarning, stacklevel=2
            )
            return list(self.iter(tag))
     
        def itertext(self):
            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）。
            """Create text iterator.
     
            The iterator loops over the element and all subelements in document
            order, returning all inner text.
     
            """
            tag = self.tag
            if not isinstance(tag, str) and tag is not None:
                return
            if self.text:
                yield self.text
            for e in self:
                yield from e.itertext()
                if e.tail:
                    yield e.tail

1.遍历XML文档中的所有内容

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][]

from xml.etree import ElementTree as ET
    ############ 解析方式一 ############
    # 打开文件，读取XML内容
    str_xml = open('xo.xml', 'r').read()
    # 将字符串解析成xml特殊对象，root代指xml文件的根节点
    root = ET.XML(str_xml) 
    ############ 解析方式二 ############
    # 直接解析xml文件
    tree = ET.parse("xo.xml")
    # 获取xml文件的根节点
    root = tree.getroot()
    # 顶层标签
    print(root.tag)
    # 遍历XML文档的第二层
    for child in root:
        # 第二层节点的标签名称和标签属性
        print(child.tag, child.attrib)
        # 遍历XML文档的第三层
        for i in child:
            # 第二层节点的标签名称和内容
            print(i.tag,i.text)
    # 输出
    country {
          'name': 'Liechtenstein'}
    rank 2
    year 2023
    gdppc 141100
    neighbor None
    neighbor None
    country {
          'name': 'Singapore'}
    rank 5
    year 2026
    gdppc 59900
    neighbor None
    country {
          'name': 'Panama'}
    rank 69
    year 2026
    gdppc 13600
    neighbor None
    neighbor None

2.遍历XML中指定的节点

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][]

from xml.etree import ElementTree as ET
    ############ 解析方式一 ############
    # 打开文件，读取XML内容
    str_xml = open('xo.xml', 'r').read()
    # 将字符串解析成xml特殊对象，root代指xml文件的根节点
    root = ET.XML(str_xml)
    ############ 解析方式二 ############
    # 直接解析xml文件
    tree = ET.parse("xo.xml")
    # 获取xml文件的根节点
    root = tree.getroot()
     
    # 顶层标签
    print(root.tag)
    # 遍历XML中所有的year节点
    for node in root.iter('year'):
        # 节点的标签名称和内容
        print(node.tag, node.text)
    # 输出
    year 2023
    year 2026
    year 2026

**3.修改节点内容**

由于修改节点时，都在内存中进行，不会影响原文件中的内容。如果想要保存修改，则会要将内存中的内容写入文件。

(1)解析字符串方式的修改和保存

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][]

from xml.etree import ElementTree as ET
    ############ 解析方式一 ############
    # 打开文件，读取XML内容
    str_xml = open('xo.xml', 'r').read()
     
    # 将字符串解析成xml特殊对象，root代指xml文件的根节点
    root = ET.XML(str_xml)
     
    ############ 操作 ############
    # 顶层标签
    print(root.tag)
    # 循环所有的year节点
    for node in root.iter('year'):
        # 将year节点中的内容自增一
        new_year = int(node.text) + 1
        node.text = str(new_year)
     
        # 设置属性
        node.set('name', 'alex')
        node.set('age', '18')
        # 删除属性
        del node.attrib['name']
     
     
    ############ 保存文件 ############
    tree = ET.ElementTree(root)
    tree.write("newnew.xml", encoding='utf-8')

(2)解析文件方式的修改和保存

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][]

from xml.etree import ElementTree as ET
    ############ 解析方式二 ############
    # 直接解析xml文件
    tree = ET.parse("xo.xml")
    # 获取xml文件的根节点
    root = tree.getroot()
    # 顶层标签
    print(root.tag)
    # 循环所有的year节点
    for node in root.iter('year'):
        # 将year节点中的内容自增一
        new_year = int(node.text) + 1
        node.text = str(new_year)
      
        # 设置属性
        node.set('name', 'alex')
        node.set('age', '18')
        # 删除属性
        del node.attrib['name']
    ############ 保存文件 ############
    tree.write("newnew.xml", encoding='utf-8')

**4.删除节点**

（1）以解析字符串方式打开XML文件的删除

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][]

from xml.etree import ElementTree as ET
    ############ 解析字符串方式打开 ############
    # 打开文件，读取XML内容
    str_xml = open('xo.xml', 'r').read()
    # 将字符串解析成xml特殊对象，root代指xml文件的根节点
    root = ET.XML(str_xml)
    # 顶层标签
    print(root.tag)
    # 遍历data下的所有country节点
    for country in root.findall('country'):
        # 获取每一个country节点下rank节点的内容
        rank = int(country.find('rank').text)
     
        if rank > 50:
            # 删除指定country节点
            root.remove(country)
    ############ 保存文件 ############
    tree = ET.ElementTree(root)
    tree.write("newnew.xml", encoding='utf-8')

（2）以解析文件方式打开的删除

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][]

from xml.etree import ElementTree as ET
    ############ 解析文件方式 ############
    # 直接解析xml文件
    tree = ET.parse("xo.xml")
    # 获取xml文件的根节点
    root = tree.getroot()
    # 顶层标签
    print(root.tag)
    # 遍历data下的所有country节点
    for country in root.findall('country'):
        # 获取每一个country节点下rank节点的内容
        rank = int(country.find('rank').text)
     
        if rank > 50:
            # 删除指定country节点
            root.remove(country)
    ############ 保存文件 ############
    tree.write("newnew.xml", encoding='utf-8')

**5.创建XML文件**

（1）创建方式一：

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][]

from xml.etree import ElementTree as ET
    # 创建根节点
    root = ET.Element("famliy")
    # 创建节点大儿子
    son1 = ET.Element('son', {
         'name': '儿1'})
    # 创建小儿子
    son2 = ET.Element('son', {
         "name": '儿2'})
    # 在大儿子中创建两个孙子
    grandson1 = ET.Element('grandson', {
         'name': '儿11'})
    grandson2 = ET.Element('grandson', {
         'name': '儿12'})
    son1.append(grandson1)
    son1.append(grandson2)
    # 把儿子添加到根节点中
    root.append(son1)
    root.append(son1)
    tree = ET.ElementTree(root)
    tree.write('oooo.xml',encoding='utf-8', short_empty_elements=False)

（2）创建方式二：

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][]

from xml.etree import ElementTree as ET
    # 创建根节点
    root = ET.Element("famliy")
    # 创建大儿子
    # son1 = ET.Element('son', {
         'name': '儿1'})
    son1 = root.makeelement('son', {
         'name': '儿1'})
    # 创建小儿子
    # son2 = ET.Element('son', {
         "name": '儿2'})
    son2 = root.makeelement('son', {
         "name": '儿2'})
    # 在大儿子中创建两个孙子
    # grandson1 = ET.Element('grandson', {
         'name': '儿11'})
    grandson1 = son1.makeelement('grandson', {
         'name': '儿11'})
    # grandson2 = ET.Element('grandson', {
         'name': '儿12'})
    grandson2 = son1.makeelement('grandson', {
         'name': '儿12'})
    son1.append(grandson1)
    son1.append(grandson2)
    # 把儿子添加到根节点中
    root.append(son1)
    root.append(son1)
    tree = ET.ElementTree(root)
    tree.write('oooo.xml',encoding='utf-8', short_empty_elements=False)

（3）创建方式三：

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][]

from xml.etree import ElementTree as ET
    # 创建根节点
    root = ET.Element("famliy")
    # 创建节点大儿子
    son1 = ET.SubElement(root, "son", attrib={
         'name': '儿1'})
    # 创建小儿子
    son2 = ET.SubElement(root, "son", attrib={
         "name": "儿2"})
    # 在大儿子中创建一个孙子
    grandson1 = ET.SubElement(son1, "age", attrib={
         'name': '儿11'})
    grandson1.text = '孙子'
    et = ET.ElementTree(root)  #生成文档对象
    et.write("test.xml", encoding="utf-8", xml_declaration=True, short_empty_elements=False)

以上创建方式的XML默认无缩减，如果要设置缩减的话，需要修改保存方式：

from xml.etree import ElementTree as ET
    from xml.dom import minidom
     
    def prettify(elem):
        """将节点转换成字符串，并添加缩进。
        """
        rough_string = ET.tostring(elem, 'utf-8')
        reparsed = minidom.parseString(rough_string)
        return reparsed.toprettyxml(indent="\t")
     
    # 创建根节点
    root = ET.Element("famliy")
    # 创建大儿子
    # son1 = ET.Element('son', {
        'name': '儿1'})
    son1 = root.makeelement('son', {
        'name': '儿1'})
    # 创建小儿子
    # son2 = ET.Element('son', {
        "name": '儿2'})
    son2 = root.makeelement('son', {
        "name": '儿2'})
    # 在大儿子中创建两个孙子
    # grandson1 = ET.Element('grandson', {
        'name': '儿11'})
    grandson1 = son1.makeelement('grandson', {
        'name': '儿11'})
    # grandson2 = ET.Element('grandson', {
        'name': '儿12'})
    grandson2 = son1.makeelement('grandson', {
        'name': '儿12'})
    son1.append(grandson1)
    son1.append(grandson2)
    # 把儿子添加到根节点中
    root.append(son1)
    root.append(son1)
    raw_str = prettify(root)
    f = open("xxxoo.xml",'w',encoding='utf-8')
    f.write(raw_str)
    f.close()

更详细学习：http://www.runoob.com/xml/xml-tutorial.html

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