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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节点功能一览表

<bookstore>  <book category="cooking">    <title lang="en">Everyday Italian</title>    <author>Giada De Laurentiis</author>    <year>2005</year>    <price>30.00</price>  </book>  <book category="children">    <title lang="en">Harry Potter</title>    <author>J K. Rowling</author>    <year>2005</year>    <price>29.99</price>  </book>  <book category="web">    <title lang="en">Learning XML</title>    <author>Erik T. Ray</author>    <year>2003</year>    <price>39.95</price>  </book></bookstore>

<data title="‘CTO" age="50">    <country name="Liechtenstein">        <rank updated="yes">2</rank>        <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>

>>> from xml.etree import ElementTree as ET>>> tree = ET.parse(‘xo.xml‘)>>> root = tree.getroot()>>> for child in root:...     print(child.tag,child.attrib)...     for grandchild in child:...         print(grandchild.tag,grandchild.text)... country {‘name‘: ‘Liechtenstein‘}rank 2year 2023gdppc 141100neighbor Noneneighbor Nonecountry {‘name‘: ‘Singapore‘}rank 5year 2026gdppc 59900neighbor Nonecountry {‘name‘: ‘Panama‘}rank 69year 2026gdppc 13600neighbor Noneneighbor None