1#@!#!123s

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Filename : ElementTree.py
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#
# ElementTree
# $Id: ElementTree.py 3440 2008-07-18 14:45:01Z fredrik $
#
# light-weight XML support for Python 2.3 and later.
#
# history (since 1.2.6):
# 2005-11-12 fl   added tostringlist/fromstringlist helpers
# 2006-07-05 fl   merged in selected changes from the 1.3 sandbox
# 2006-07-05 fl   removed support for 2.1 and earlier
# 2007-06-21 fl   added deprecation/future warnings
# 2007-08-25 fl   added doctype hook, added parser version attribute etc
# 2007-08-26 fl   added new serializer code (better namespace handling, etc)
# 2007-08-27 fl   warn for broken /tag searches on tree level
# 2007-09-02 fl   added html/text methods to serializer (experimental)
# 2007-09-05 fl   added method argument to tostring/tostringlist
# 2007-09-06 fl   improved error handling
# 2007-09-13 fl   added itertext, iterfind; assorted cleanups
# 2007-12-15 fl   added C14N hooks, copy method (experimental)
#
# Copyright (c) 1999-2008 by Fredrik Lundh.  All rights reserved.
#
# fredrik@pythonware.com
# http://www.pythonware.com
#
# --------------------------------------------------------------------
# The ElementTree toolkit is
#
# Copyright (c) 1999-2008 by Fredrik Lundh
#
# By obtaining, using, and/or copying this software and/or its
# associated documentation, you agree that you have read, understood,
# and will comply with the following terms and conditions:
#
# Permission to use, copy, modify, and distribute this software and
# its associated documentation for any purpose and without fee is
# hereby granted, provided that the above copyright notice appears in
# all copies, and that both that copyright notice and this permission
# notice appear in supporting documentation, and that the name of
# Secret Labs AB or the author not be used in advertising or publicity
# pertaining to distribution of the software without specific, written
# prior permission.
#
# SECRET LABS AB AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD
# TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANT-
# ABILITY AND FITNESS.  IN NO EVENT SHALL SECRET LABS AB OR THE AUTHOR
# BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY
# DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
# WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
# ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
# OF THIS SOFTWARE.
# --------------------------------------------------------------------

# Licensed to PSF under a Contributor Agreement.
# See http://www.python.org/psf/license for licensing details.

__all__ = [
    # public symbols
    "Comment",
    "dump",
    "Element", "ElementTree",
    "fromstring", "fromstringlist",
    "iselement", "iterparse",
    "parse", "ParseError",
    "PI", "ProcessingInstruction",
    "QName",
    "SubElement",
    "tostring", "tostringlist",
    "TreeBuilder",
    "VERSION",
    "XML", "XMLID",
    "XMLParser", "XMLTreeBuilder",
    "register_namespace",
    ]

VERSION = "1.3.0"

##
# The <b>Element</b> type is a flexible container object, designed to
# store hierarchical data structures in memory. The type can be
# described as a cross between a list and a dictionary.
# <p>
# Each element has a number of properties associated with it:
# <ul>
# <li>a <i>tag</i>. This is a string identifying what kind of data
# this element represents (the element type, in other words).</li>
# <li>a number of <i>attributes</i>, stored in a Python dictionary.</li>
# <li>a <i>text</i> string.</li>
# <li>an optional <i>tail</i> string.</li>
# <li>a number of <i>child elements</i>, stored in a Python sequence</li>
# </ul>
#
# To create an element instance, use the {@link #Element} constructor
# or the {@link #SubElement} factory function.
# <p>
# The {@link #ElementTree} class can be used to wrap an element
# structure, and convert it from and to XML.
##

import sys
import re
import warnings
import io
import contextlib

from . import ElementPath


##
# Parser error.  This is a subclass of <b>SyntaxError</b>.
# <p>
# In addition to the exception value, an exception instance contains a
# specific exception code in the <b>code</b> attribute, and the line and
# column of the error in the <b>position</b> attribute.

class ParseError(SyntaxError):
    pass

# --------------------------------------------------------------------

##
# Checks if an object appears to be a valid element object.
#
# @param An element instance.
# @return A true value if this is an element object.
# @defreturn flag

def iselement(element):
    # FIXME: not sure about this;
    # isinstance(element, Element) or look for tag/attrib/text attributes
    return hasattr(element, 'tag')

##
# Element class.  This class defines the Element interface, and
# provides a reference implementation of this interface.
# <p>
# The element name, attribute names, and attribute values can be
# either ASCII strings (ordinary Python strings containing only 7-bit
# ASCII characters) or Unicode strings.
#
# @param tag The element name.
# @param attrib An optional dictionary, containing element attributes.
# @param **extra Additional attributes, given as keyword arguments.
# @see Element
# @see SubElement
# @see Comment
# @see ProcessingInstruction

class Element:
    # <tag attrib>text<child/>...</tag>tail

    ##
    # (Attribute) Element tag.

    tag = None

    ##
    # (Attribute) Element attribute dictionary.  Where possible, use
    # {@link #Element.get},
    # {@link #Element.set},
    # {@link #Element.keys}, and
    # {@link #Element.items} to access
    # element attributes.

    attrib = None

    ##
    # (Attribute) Text before first subelement.  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.

    text = None

    ##
    # (Attribute) 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.

    tail = None # text after end tag, if any

    # constructor

    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 "<Element %s at 0x%x>" % (repr(self.tag), id(self))

    ##
    # Creates a new element object of the same type as this element.
    #
    # @param tag Element tag.
    # @param attrib Element attributes, given as a dictionary.
    # @return A new element instance.

    def makeelement(self, tag, attrib):
        return self.__class__(tag, attrib)

    ##
    # (Experimental) Copies the current element.  This creates a
    # shallow copy; subelements will be shared with the original tree.
    #
    # @return A new element instance.

    def copy(self):
        elem = self.makeelement(self.tag, self.attrib)
        elem.text = self.text
        elem.tail = self.tail
        elem[:] = self
        return elem

    ##
    # Returns the number of subelements.  Note that this only counts
    # full elements; to check if there's any content in an element, you
    # have to check both the length and the <b>text</b> attribute.
    #
    # @return The number of subelements.

    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

    ##
    # Returns the given subelement, by index.
    #
    # @param index What subelement to return.
    # @return The given subelement.
    # @exception IndexError If the given element does not exist.

    def __getitem__(self, index):
        return self._children[index]

    ##
    # Replaces the given subelement, by index.
    #
    # @param index What subelement to replace.
    # @param element The new element value.
    # @exception IndexError If the given element does not exist.

    def __setitem__(self, index, element):
        # if isinstance(index, slice):
        #     for elt in element:
        #         assert iselement(elt)
        # else:
        #     assert iselement(element)
        self._children[index] = element

    ##
    # Deletes the given subelement, by index.
    #
    # @param index What subelement to delete.
    # @exception IndexError If the given element does not exist.

    def __delitem__(self, index):
        del self._children[index]

    ##
    # Adds a subelement to the end of this element.  In document order,
    # the new element will appear after the last existing subelement (or
    # directly after the text, if it's the first subelement), but before
    # the end tag for this element.
    #
    # @param element The element to add.

    def append(self, element):
        self._assert_is_element(element)
        self._children.append(element)

    ##
    # Appends subelements from a sequence.
    #
    # @param elements A sequence object with zero or more elements.
    # @since 1.3

    def extend(self, elements):
        for element in elements:
            self._assert_is_element(element)
        self._children.extend(elements)

    ##
    # Inserts a subelement at the given position in this element.
    #
    # @param index Where to insert the new subelement.

    def insert(self, index, element):
        self._assert_is_element(element)
        self._children.insert(index, element)

    def _assert_is_element(self, e):
        # Need to refer to the actual Python implementation, not the
        # shadowing C implementation.
        if not isinstance(e, _Element):
            raise TypeError('expected an Element, not %s' % type(e).__name__)

    ##
    # Removes a matching subelement.  Unlike the <b>find</b> methods,
    # this method compares elements based on identity, not on tag
    # value or contents.  To remove subelements by other means, the
    # easiest way is often to use a list comprehension to select what
    # elements to keep, and use slice assignment to update the parent
    # element.
    #
    # @param element What element to remove.
    # @exception ValueError If a matching element could not be found.

    def remove(self, element):
        # assert iselement(element)
        self._children.remove(element)

    ##
    # (Deprecated) Returns all subelements.  The elements are returned
    # in document order.
    #
    # @return A list of subelements.
    # @defreturn list of Element instances

    def getchildren(self):
        warnings.warn(
            "This method will be removed in future versions.  "
            "Use 'list(elem)' or iteration over elem instead.",
            DeprecationWarning, stacklevel=2
            )
        return self._children

    ##
    # Finds the first matching subelement, by tag name or path.
    #
    # @param path What element to look for.
    # @keyparam namespaces Optional namespace prefix map.
    # @return The first matching element, or None if no element was found.
    # @defreturn Element or None

    def find(self, path, namespaces=None):
        return ElementPath.find(self, path, namespaces)

    ##
    # Finds text for the first matching subelement, by tag name or path.
    #
    # @param path What element to look for.
    # @param default What to return if the element was not found.
    # @keyparam namespaces Optional namespace prefix map.
    # @return 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.
    # @defreturn string

    def findtext(self, path, default=None, namespaces=None):
        return ElementPath.findtext(self, path, default, namespaces)

    ##
    # Finds all matching subelements, by tag name or path.
    #
    # @param path What element to look for.
    # @keyparam namespaces Optional namespace prefix map.
    # @return A list or other sequence containing all matching elements,
    #    in document order.
    # @defreturn list of Element instances

    def findall(self, path, namespaces=None):
        return ElementPath.findall(self, path, namespaces)

    ##
    # Finds all matching subelements, by tag name or path.
    #
    # @param path What element to look for.
    # @keyparam namespaces Optional namespace prefix map.
    # @return An iterator or sequence containing all matching elements,
    #    in document order.
    # @defreturn a generated sequence of Element instances

    def iterfind(self, path, namespaces=None):
        return ElementPath.iterfind(self, path, namespaces)

    ##
    # Resets an element.  This function removes all subelements, clears
    # all attributes, and sets the <b>text</b> and <b>tail</b> attributes
    # to None.

    def clear(self):
        self.attrib.clear()
        self._children = []
        self.text = self.tail = None

    ##
    # Gets an element attribute.  Equivalent to <b>attrib.get</b>, but
    # some implementations may handle this a bit more efficiently.
    #
    # @param key What attribute to look for.
    # @param default What to return if the attribute was not found.
    # @return The attribute value, or the default value, if the
    #     attribute was not found.
    # @defreturn string or None

    def get(self, key, default=None):
        return self.attrib.get(key, default)

    ##
    # Sets an element attribute.  Equivalent to <b>attrib[key] = value</b>,
    # but some implementations may handle this a bit more efficiently.
    #
    # @param key What attribute to set.
    # @param value The attribute value.

    def set(self, key, value):
        self.attrib[key] = value

    ##
    # Gets a list of attribute names.  The names are returned in an
    # arbitrary order (just like for an ordinary Python dictionary).
    # Equivalent to <b>attrib.keys()</b>.
    #
    # @return A list of element attribute names.
    # @defreturn list of strings

    def keys(self):
        return self.attrib.keys()

    ##
    # Gets element attributes, as a sequence.  The attributes are
    # returned in an arbitrary order.  Equivalent to <b>attrib.items()</b>.
    #
    # @return A list of (name, value) tuples for all attributes.
    # @defreturn list of (string, string) tuples

    def items(self):
        return self.attrib.items()

    ##
    # Creates a tree iterator.  The iterator loops over this element
    # and all subelements, in document order, and returns all elements
    # with a matching tag.
    # <p>
    # 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.
    #
    # @param tag What tags to look for (default is to return all elements).
    # @return An iterator containing all the matching elements.
    # @defreturn iterator

    def iter(self, tag=None):
        if tag == "*":
            tag = None
        if tag is None or self.tag == tag:
            yield self
        for e in self._children:
            for e in e.iter(tag):
                yield e

    # 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))

    ##
    # Creates a text iterator.  The iterator loops over this element
    # and all subelements, in document order, and returns all inner
    # text.
    #
    # @return An iterator containing all inner text.
    # @defreturn iterator

    def itertext(self):
        tag = self.tag
        if not isinstance(tag, str) and tag is not None:
            return
        if self.text:
            yield self.text
        for e in self:
            for s in e.itertext():
                yield s
            if e.tail:
                yield e.tail

# compatibility
_Element = _ElementInterface = Element

##
# Subelement factory.  This function creates an element instance, and
# appends it to an existing element.
# <p>
# The element name, attribute names, and attribute values can be
# either 8-bit ASCII strings or Unicode strings.
#
# @param parent The parent element.
# @param tag The subelement name.
# @param attrib An optional dictionary, containing element attributes.
# @param **extra Additional attributes, given as keyword arguments.
# @return An element instance.
# @defreturn Element

def SubElement(parent, tag, attrib={}, **extra):
    attrib = attrib.copy()
    attrib.update(extra)
    element = parent.makeelement(tag, attrib)
    parent.append(element)
    return element

##
# Comment element factory.  This factory function creates a special
# element that will be serialized as an XML comment by the standard
# serializer.
# <p>
# The comment string can be either an 8-bit ASCII string or a Unicode
# string.
#
# @param text A string containing the comment string.
# @return An element instance, representing a comment.
# @defreturn Element

def Comment(text=None):
    element = Element(Comment)
    element.text = text
    return element

##
# PI element factory.  This factory function creates a special element
# that will be serialized as an XML processing instruction by the standard
# serializer.
#
# @param target A string containing the PI target.
# @param text A string containing the PI contents, if any.
# @return An element instance, representing a PI.
# @defreturn Element

def ProcessingInstruction(target, text=None):
    element = Element(ProcessingInstruction)
    element.text = target
    if text:
        element.text = element.text + " " + text
    return element

PI = ProcessingInstruction

##
# QName wrapper.  This can be used to wrap a QName attribute value, in
# order to get proper namespace handling on output.
#
# @param text A string containing the QName value, in the form {uri}local,
#     or, if the tag argument is given, the URI part of a QName.
# @param tag Optional tag.  If given, the first argument is interpreted as
#     an URI, and this argument is interpreted as a local name.
# @return An opaque object, representing the QName.

class QName:
    def __init__(self, text_or_uri, tag=None):
        if tag:
            text_or_uri = "{%s}%s" % (text_or_uri, tag)
        self.text = text_or_uri
    def __str__(self):
        return self.text
    def __repr__(self):
        return '<QName %r>' % (self.text,)
    def __hash__(self):
        return hash(self.text)
    def __le__(self, other):
        if isinstance(other, QName):
            return self.text <= other.text
        return self.text <= other
    def __lt__(self, other):
        if isinstance(other, QName):
            return self.text < other.text
        return self.text < other
    def __ge__(self, other):
        if isinstance(other, QName):
            return self.text >= other.text
        return self.text >= other
    def __gt__(self, other):
        if isinstance(other, QName):
            return self.text > other.text
        return self.text > other
    def __eq__(self, other):
        if isinstance(other, QName):
            return self.text == other.text
        return self.text == other
    def __ne__(self, other):
        if isinstance(other, QName):
            return self.text != other.text
        return self.text != other

# --------------------------------------------------------------------

##
# ElementTree wrapper class.  This class represents an entire element
# hierarchy, and adds some extra support for serialization to and from
# standard XML.
#
# @param element Optional root element.
# @keyparam file Optional file handle or file name.  If given, the
#     tree is initialized with the contents of this XML file.

class ElementTree:

    def __init__(self, element=None, file=None):
        # assert element is None or iselement(element)
        self._root = element # first node
        if file:
            self.parse(file)

    ##
    # Gets the root element for this tree.
    #
    # @return An element instance.
    # @defreturn Element

    def getroot(self):
        return self._root

    ##
    # 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.
    #
    # @param element An element instance.

    def _setroot(self, element):
        # assert iselement(element)
        self._root = element

    ##
    # Loads an external XML document into this element tree.
    #
    # @param source A file name or file object.  If a file object is
    #     given, it only has to implement a <b>read(n)</b> method.
    # @keyparam parser An optional parser instance.  If not given, the
    #     standard {@link XMLParser} parser is used.
    # @return The document root element.
    # @defreturn Element
    # @exception ParseError If the parser fails to parse the document.

    def parse(self, source, parser=None):
        close_source = False
        if not hasattr(source, "read"):
            source = open(source, "rb")
            close_source = True
        try:
            if not parser:
                parser = XMLParser(target=TreeBuilder())
            while 1:
                data = source.read(65536)
                if not data:
                    break
                parser.feed(data)
            self._root = parser.close()
            return self._root
        finally:
            if close_source:
                source.close()

    ##
    # Creates a tree iterator for the root element.  The iterator loops
    # over all elements in this tree, in document order.
    #
    # @param tag What tags to look for (default is to return all elements)
    # @return An iterator.
    # @defreturn iterator

    def iter(self, tag=None):
        # assert self._root is not None
        return self._root.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 'tree.iter()' or 'list(tree.iter())' instead.",
            PendingDeprecationWarning, stacklevel=2
        )
        return list(self.iter(tag))

    ##
    # Same as getroot().find(path), starting at the root of the tree.
    #
    # @param path What element to look for.
    # @keyparam namespaces Optional namespace prefix map.
    # @return The first matching element, or None if no element was found.
    # @defreturn Element or None

    def find(self, path, namespaces=None):
        # assert self._root is not None
        if path[:1] == "/":
            path = "." + path
            warnings.warn(
                "This search is broken in 1.3 and earlier, and will be "
                "fixed in a future version.  If you rely on the current "
                "behaviour, change it to %r" % path,
                FutureWarning, stacklevel=2
                )
        return self._root.find(path, namespaces)

    ##
    # Same as getroot().findtext(path), starting at the root of the tree.
    #
    # @param path What element to look for.
    # @param default What to return if the element was not found.
    # @keyparam namespaces Optional namespace prefix map.
    # @return 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.
    # @defreturn string

    def findtext(self, path, default=None, namespaces=None):
        # assert self._root is not None
        if path[:1] == "/":
            path = "." + path
            warnings.warn(
                "This search is broken in 1.3 and earlier, and will be "
                "fixed in a future version.  If you rely on the current "
                "behaviour, change it to %r" % path,
                FutureWarning, stacklevel=2
                )
        return self._root.findtext(path, default, namespaces)

    ##
    # Same as getroot().findall(path), starting at the root of the tree.
    #
    # @param path What element to look for.
    # @keyparam namespaces Optional namespace prefix map.
    # @return A list or iterator containing all matching elements,
    #    in document order.
    # @defreturn list of Element instances

    def findall(self, path, namespaces=None):
        # assert self._root is not None
        if path[:1] == "/":
            path = "." + path
            warnings.warn(
                "This search is broken in 1.3 and earlier, and will be "
                "fixed in a future version.  If you rely on the current "
                "behaviour, change it to %r" % path,
                FutureWarning, stacklevel=2
                )
        return self._root.findall(path, namespaces)

    ##
    # Finds all matching subelements, by tag name or path.
    # Same as getroot().iterfind(path).
    #
    # @param path What element to look for.
    # @keyparam namespaces Optional namespace prefix map.
    # @return An iterator or sequence containing all matching elements,
    #    in document order.
    # @defreturn a generated sequence of Element instances

    def iterfind(self, path, namespaces=None):
        # assert self._root is not None
        if path[:1] == "/":
            path = "." + path
            warnings.warn(
                "This search is broken in 1.3 and earlier, and will be "
                "fixed in a future version.  If you rely on the current "
                "behaviour, change it to %r" % path,
                FutureWarning, stacklevel=2
                )
        return self._root.iterfind(path, namespaces)

    ##
    # Writes the element tree to a file, as XML.
    #
    # @def write(file, **options)
    # @param file A file name, or a file object opened for writing.
    # @param **options Options, given as keyword arguments.
    # @keyparam encoding Optional output encoding (default is US-ASCII).
    #     Use "unicode" to return a Unicode string.
    # @keyparam 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 or Unicode.  None is default.
    # @keyparam default_namespace Sets the default XML namespace (for "xmlns").
    # @keyparam method Optional output method ("xml", "html", "text" or
    #     "c14n"; default is "xml").

    def write(self, file_or_filename,
              encoding=None,
              xml_declaration=None,
              default_namespace=None,
              method=None):
        if not method:
            method = "xml"
        elif method not in _serialize:
            raise ValueError("unknown method %r" % method)
        if not encoding:
            if method == "c14n":
                encoding = "utf-8"
            else:
                encoding = "us-ascii"
        else:
            encoding = encoding.lower()
        with _get_writer(file_or_filename, encoding) as write:
            if method == "xml" and (xml_declaration or
                    (xml_declaration is None and
                     encoding not in ("utf-8", "us-ascii", "unicode"))):
                declared_encoding = encoding
                if encoding == "unicode":
                    # Retrieve the default encoding for the xml declaration
                    import locale
                    declared_encoding = locale.getpreferredencoding()
                write("<?xml version='1.0' encoding='%s'?>\n" % (
                    declared_encoding,))
            if method == "text":
                _serialize_text(write, self._root)
            else:
                qnames, namespaces = _namespaces(self._root, default_namespace)
                serialize = _serialize[method]
                serialize(write, self._root, qnames, namespaces)

    def write_c14n(self, file):
        # lxml.etree compatibility.  use output method instead
        return self.write(file, method="c14n")

# --------------------------------------------------------------------
# serialization support

@contextlib.contextmanager
def _get_writer(file_or_filename, encoding):
    # returns text write method and release all resources after using
    try:
        write = file_or_filename.write
    except AttributeError:
        # file_or_filename is a file name
        if encoding == "unicode":
            file = open(file_or_filename, "w")
        else:
            file = open(file_or_filename, "w", encoding=encoding,
                        errors="xmlcharrefreplace")
        with file:
            yield file.write
    else:
        # file_or_filename is a file-like object
        # encoding determines if it is a text or binary writer
        if encoding == "unicode":
            # use a text writer as is
            yield write
        else:
            # wrap a binary writer with TextIOWrapper
            with contextlib.ExitStack() as stack:
                if isinstance(file_or_filename, io.BufferedIOBase):
                    file = file_or_filename
                elif isinstance(file_or_filename, io.RawIOBase):
                    file = io.BufferedWriter(file_or_filename)
                    # Keep the original file open when the BufferedWriter is
                    # destroyed
                    stack.callback(file.detach)
                else:
                    # This is to handle passed objects that aren't in the
                    # IOBase hierarchy, but just have a write method
                    file = io.BufferedIOBase()
                    file.writable = lambda: True
                    file.write = write
                    try:
                        # TextIOWrapper uses this methods to determine
                        # if BOM (for UTF-16, etc) should be added
                        file.seekable = file_or_filename.seekable
                        file.tell = file_or_filename.tell
                    except AttributeError:
                        pass
                file = io.TextIOWrapper(file,
                                        encoding=encoding,
                                        errors="xmlcharrefreplace",
                                        newline="\n")
                # Keep the original file open when the TextIOWrapper is
                # destroyed
                stack.callback(file.detach)
                yield file.write

def _namespaces(elem, default_namespace=None):
    # identify namespaces used in this tree

    # maps qnames to *encoded* prefix:local names
    qnames = {None: None}

    # maps uri:s to prefixes
    namespaces = {}
    if default_namespace:
        namespaces[default_namespace] = ""

    def add_qname(qname):
        # calculate serialized qname representation
        try:
            if qname[:1] == "{":
                uri, tag = qname[1:].rsplit("}", 1)
                prefix = namespaces.get(uri)
                if prefix is None:
                    prefix = _namespace_map.get(uri)
                    if prefix is None:
                        prefix = "ns%d" % len(namespaces)
                    if prefix != "xml":
                        namespaces[uri] = prefix
                if prefix:
                    qnames[qname] = "%s:%s" % (prefix, tag)
                else:
                    qnames[qname] = tag # default element
            else:
                if default_namespace:
                    # FIXME: can this be handled in XML 1.0?
                    raise ValueError(
                        "cannot use non-qualified names with "
                        "default_namespace option"
                        )
                qnames[qname] = qname
        except TypeError:
            _raise_serialization_error(qname)

    # populate qname and namespaces table
    for elem in elem.iter():
        tag = elem.tag
        if isinstance(tag, QName):
            if tag.text not in qnames:
                add_qname(tag.text)
        elif isinstance(tag, str):
            if tag not in qnames:
                add_qname(tag)
        elif tag is not None and tag is not Comment and tag is not PI:
            _raise_serialization_error(tag)
        for key, value in elem.items():
            if isinstance(key, QName):
                key = key.text
            if key not in qnames:
                add_qname(key)
            if isinstance(value, QName) and value.text not in qnames:
                add_qname(value.text)
        text = elem.text
        if isinstance(text, QName) and text.text not in qnames:
            add_qname(text.text)
    return qnames, namespaces

def _serialize_xml(write, elem, qnames, namespaces):
    tag = elem.tag
    text = elem.text
    if tag is Comment:
        write("<!--%s-->" % text)
    elif tag is ProcessingInstruction:
        write("<?%s?>" % text)
    else:
        tag = qnames[tag]
        if tag is None:
            if text:
                write(_escape_cdata(text))
            for e in elem:
                _serialize_xml(write, e, qnames, None)
        else:
            write("<" + tag)
            items = list(elem.items())
            if items or namespaces:
                if namespaces:
                    for v, k in sorted(namespaces.items(),
                                       key=lambda x: x[1]):  # sort on prefix
                        if k:
                            k = ":" + k
                        write(" xmlns%s=\"%s\"" % (
                            k,
                            _escape_attrib(v)
                            ))
                for k, v in sorted(items):  # lexical order
                    if isinstance(k, QName):
                        k = k.text
                    if isinstance(v, QName):
                        v = qnames[v.text]
                    else:
                        v = _escape_attrib(v)
                    write(" %s=\"%s\"" % (qnames[k], v))
            if text or len(elem):
                write(">")
                if text:
                    write(_escape_cdata(text))
                for e in elem:
                    _serialize_xml(write, e, qnames, None)
                write("</" + tag + ">")
            else:
                write(" />")
    if elem.tail:
        write(_escape_cdata(elem.tail))

HTML_EMPTY = ("area", "base", "basefont", "br", "col", "frame", "hr",
              "img", "input", "isindex", "link", "meta", "param")

try:
    HTML_EMPTY = set(HTML_EMPTY)
except NameError:
    pass

def _serialize_html(write, elem, qnames, namespaces):
    tag = elem.tag
    text = elem.text
    if tag is Comment:
        write("<!--%s-->" % _escape_cdata(text))
    elif tag is ProcessingInstruction:
        write("<?%s?>" % _escape_cdata(text))
    else:
        tag = qnames[tag]
        if tag is None:
            if text:
                write(_escape_cdata(text))
            for e in elem:
                _serialize_html(write, e, qnames, None)
        else:
            write("<" + tag)
            items = list(elem.items())
            if items or namespaces:
                if namespaces:
                    for v, k in sorted(namespaces.items(),
                                       key=lambda x: x[1]):  # sort on prefix
                        if k:
                            k = ":" + k
                        write(" xmlns%s=\"%s\"" % (
                            k,
                            _escape_attrib(v)
                            ))
                for k, v in sorted(items):  # lexical order
                    if isinstance(k, QName):
                        k = k.text
                    if isinstance(v, QName):
                        v = qnames[v.text]
                    else:
                        v = _escape_attrib_html(v)
                    # FIXME: handle boolean attributes
                    write(" %s=\"%s\"" % (qnames[k], v))
            write(">")
            ltag = tag.lower()
            if text:
                if ltag == "script" or ltag == "style":
                    write(text)
                else:
                    write(_escape_cdata(text))
            for e in elem:
                _serialize_html(write, e, qnames, None)
            if ltag not in HTML_EMPTY:
                write("</" + tag + ">")
    if elem.tail:
        write(_escape_cdata(elem.tail))

def _serialize_text(write, elem):
    for part in elem.itertext():
        write(part)
    if elem.tail:
        write(elem.tail)

_serialize = {
    "xml": _serialize_xml,
    "html": _serialize_html,
    "text": _serialize_text,
# this optional method is imported at the end of the module
#   "c14n": _serialize_c14n,
}

##
# Registers a namespace prefix.  The registry is global, and any
# existing mapping for either the given prefix or the namespace URI
# will be removed.
#
# @param prefix Namespace prefix.
# @param uri Namespace uri.  Tags and attributes in this namespace
#     will be serialized with the given prefix, if at all possible.
# @exception ValueError If the prefix is reserved, or is otherwise
#     invalid.

def register_namespace(prefix, uri):
    if re.match("ns\d+$", prefix):
        raise ValueError("Prefix format reserved for internal use")
    for k, v in list(_namespace_map.items()):
        if k == uri or v == prefix:
            del _namespace_map[k]
    _namespace_map[uri] = prefix

_namespace_map = {
    # "well-known" namespace prefixes
    "http://www.w3.org/XML/1998/namespace": "xml",
    "http://www.w3.org/1999/xhtml": "html",
    "http://www.w3.org/1999/02/22-rdf-syntax-ns#": "rdf",
    "http://schemas.xmlsoap.org/wsdl/": "wsdl",
    # xml schema
    "http://www.w3.org/2001/XMLSchema": "xs",
    "http://www.w3.org/2001/XMLSchema-instance": "xsi",
    # dublin core
    "http://purl.org/dc/elements/1.1/": "dc",
}
# For tests and troubleshooting
register_namespace._namespace_map = _namespace_map

def _raise_serialization_error(text):
    raise TypeError(
        "cannot serialize %r (type %s)" % (text, type(text).__name__)
        )

def _escape_cdata(text):
    # escape character data
    try:
        # it's worth avoiding do-nothing calls for strings that are
        # shorter than 500 character, or so.  assume that's, by far,
        # the most common case in most applications.
        if "&" in text:
            text = text.replace("&", "&amp;")
        if "<" in text:
            text = text.replace("<", "&lt;")
        if ">" in text:
            text = text.replace(">", "&gt;")
        return text
    except (TypeError, AttributeError):
        _raise_serialization_error(text)

def _escape_attrib(text):
    # escape attribute value
    try:
        if "&" in text:
            text = text.replace("&", "&amp;")
        if "<" in text:
            text = text.replace("<", "&lt;")
        if ">" in text:
            text = text.replace(">", "&gt;")
        if "\"" in text:
            text = text.replace("\"", "&quot;")
        if "\n" in text:
            text = text.replace("\n", "&#10;")
        return text
    except (TypeError, AttributeError):
        _raise_serialization_error(text)

def _escape_attrib_html(text):
    # escape attribute value
    try:
        if "&" in text:
            text = text.replace("&", "&amp;")
        if ">" in text:
            text = text.replace(">", "&gt;")
        if "\"" in text:
            text = text.replace("\"", "&quot;")
        return text
    except (TypeError, AttributeError):
        _raise_serialization_error(text)

# --------------------------------------------------------------------

##
# Generates a string representation of an XML element, including all
# subelements.  If encoding is "unicode", the return type is a string;
# otherwise it is a bytes array.
#
# @param element An Element instance.
# @keyparam encoding Optional output encoding (default is US-ASCII).
#     Use "unicode" to return a Unicode string.
# @keyparam method Optional output method ("xml", "html", "text" or
#     "c14n"; default is "xml").
# @return An (optionally) encoded string containing the XML data.
# @defreturn string

def tostring(element, encoding=None, method=None):
    stream = io.StringIO() if encoding == 'unicode' else io.BytesIO()
    ElementTree(element).write(stream, encoding, method=method)
    return stream.getvalue()

##
# Generates a string representation of an XML element, including all
# subelements.
#
# @param element An Element instance.
# @keyparam encoding Optional output encoding (default is US-ASCII).
#     Use "unicode" to return a Unicode string.
# @keyparam method Optional output method ("xml", "html", "text" or
#     "c14n"; default is "xml").
# @return A sequence object containing the XML data.
# @defreturn sequence
# @since 1.3

class _ListDataStream(io.BufferedIOBase):
    """ An auxiliary stream accumulating into a list reference
    """
    def __init__(self, lst):
        self.lst = lst

    def writable(self):
        return True

    def seekable(self):
        return True

    def write(self, b):
        self.lst.append(b)

    def tell(self):
        return len(self.lst)

def tostringlist(element, encoding=None, method=None):
    lst = []
    stream = _ListDataStream(lst)
    ElementTree(element).write(stream, encoding, method=method)
    return lst

##
# Writes an element tree or element structure to sys.stdout.  This
# function should be used for debugging only.
# <p>
# The exact output format is implementation dependent.  In this
# version, it's written as an ordinary XML file.
#
# @param elem An element tree or an individual element.

def dump(elem):
    # debugging
    if not isinstance(elem, ElementTree):
        elem = ElementTree(elem)
    elem.write(sys.stdout, encoding="unicode")
    tail = elem.getroot().tail
    if not tail or tail[-1] != "\n":
        sys.stdout.write("\n")

# --------------------------------------------------------------------
# parsing

##
# Parses an XML document into an element tree.
#
# @param source A filename or file object containing XML data.
# @param parser An optional parser instance.  If not given, the
#     standard {@link XMLParser} parser is used.
# @return An ElementTree instance

def parse(source, parser=None):
    tree = ElementTree()
    tree.parse(source, parser)
    return tree

##
# Parses an XML document into an element tree incrementally, and reports
# what's going on to the user.
#
# @param source A filename or file object containing XML data.
# @param events A list of events to report back.  If omitted, only "end"
#     events are reported.
# @param parser An optional parser instance.  If not given, the
#     standard {@link XMLParser} parser is used.
# @return A (event, elem) iterator.

def iterparse(source, events=None, parser=None):
    close_source = False
    if not hasattr(source, "read"):
        source = open(source, "rb")
        close_source = True
    if not parser:
        parser = XMLParser(target=TreeBuilder())
    return _IterParseIterator(source, events, parser, close_source)

class _IterParseIterator:

    def __init__(self, source, events, parser, close_source=False):
        self._file = source
        self._close_file = close_source
        self._events = []
        self._index = 0
        self._error = None
        self.root = self._root = None
        self._parser = parser
        # wire up the parser for event reporting
        parser = self._parser._parser
        append = self._events.append
        if events is None:
            events = ["end"]
        for event in events:
            if event == "start":
                try:
                    parser.ordered_attributes = 1
                    parser.specified_attributes = 1
                    def handler(tag, attrib_in, event=event, append=append,
                                start=self._parser._start_list):
                        append((event, start(tag, attrib_in)))
                    parser.StartElementHandler = handler
                except AttributeError:
                    def handler(tag, attrib_in, event=event, append=append,
                                start=self._parser._start):
                        append((event, start(tag, attrib_in)))
                    parser.StartElementHandler = handler
            elif event == "end":
                def handler(tag, event=event, append=append,
                            end=self._parser._end):
                    append((event, end(tag)))
                parser.EndElementHandler = handler
            elif event == "start-ns":
                def handler(prefix, uri, event=event, append=append):
                    append((event, (prefix or "", uri or "")))
                parser.StartNamespaceDeclHandler = handler
            elif event == "end-ns":
                def handler(prefix, event=event, append=append):
                    append((event, None))
                parser.EndNamespaceDeclHandler = handler
            else:
                raise ValueError("unknown event %r" % event)

    def __next__(self):
        while 1:
            try:
                item = self._events[self._index]
                self._index += 1
                return item
            except IndexError:
                pass
            if self._error:
                e = self._error
                self._error = None
                raise e
            if self._parser is None:
                self.root = self._root
                if self._close_file:
                    self._file.close()
                raise StopIteration
            # load event buffer
            del self._events[:]
            self._index = 0
            data = self._file.read(16384)
            if data:
                try:
                    self._parser.feed(data)
                except SyntaxError as exc:
                    self._error = exc
            else:
                self._root = self._parser.close()
                self._parser = None

    def __iter__(self):
        return self

##
# Parses an XML document from a string constant.  This function can
# be used to embed "XML literals" in Python code.
#
# @param source A string containing XML data.
# @param parser An optional parser instance.  If not given, the
#     standard {@link XMLParser} parser is used.
# @return An Element instance.
# @defreturn Element

def XML(text, parser=None):
    if not parser:
        parser = XMLParser(target=TreeBuilder())
    parser.feed(text)
    return parser.close()

##
# Parses an XML document from a string constant, and also returns
# a dictionary which maps from element id:s to elements.
#
# @param source A string containing XML data.
# @param parser An optional parser instance.  If not given, the
#     standard {@link XMLParser} parser is used.
# @return A tuple containing an Element instance and a dictionary.
# @defreturn (Element, dictionary)

def XMLID(text, parser=None):
    if not parser:
        parser = XMLParser(target=TreeBuilder())
    parser.feed(text)
    tree = parser.close()
    ids = {}
    for elem in tree.iter():
        id = elem.get("id")
        if id:
            ids[id] = elem
    return tree, ids

##
# Parses an XML document from a string constant.  Same as {@link #XML}.
#
# @def fromstring(text)
# @param source A string containing XML data.
# @return An Element instance.
# @defreturn Element

fromstring = XML

##
# Parses an XML document from a sequence of string fragments.
#
# @param sequence A list or other sequence containing XML data fragments.
# @param parser An optional parser instance.  If not given, the
#     standard {@link XMLParser} parser is used.
# @return An Element instance.
# @defreturn Element
# @since 1.3

def fromstringlist(sequence, parser=None):
    if not parser:
        parser = XMLParser(target=TreeBuilder())
    for text in sequence:
        parser.feed(text)
    return parser.close()

# --------------------------------------------------------------------

##
# Generic element structure builder.  This builder converts a sequence
# of {@link #TreeBuilder.start}, {@link #TreeBuilder.data}, and {@link
# #TreeBuilder.end} method calls to a well-formed element structure.
# <p>
# You can use this class to build an element structure using a custom XML
# parser, or a parser for some other XML-like format.
#
# @param element_factory Optional element factory.  This factory
#    is called to create new Element instances, as necessary.

class TreeBuilder:

    def __init__(self, element_factory=None):
        self._data = [] # data collector
        self._elem = [] # element stack
        self._last = None # last element
        self._tail = None # true if we're after an end tag
        if element_factory is None:
            element_factory = Element
        self._factory = element_factory

    ##
    # Flushes the builder buffers, and returns the toplevel document
    # element.
    #
    # @return An Element instance.
    # @defreturn Element

    def close(self):
        assert len(self._elem) == 0, "missing end tags"
        assert self._last is not None, "missing toplevel element"
        return self._last

    def _flush(self):
        if self._data:
            if self._last is not None:
                text = "".join(self._data)
                if self._tail:
                    assert self._last.tail is None, "internal error (tail)"
                    self._last.tail = text
                else:
                    assert self._last.text is None, "internal error (text)"
                    self._last.text = text
            self._data = []

    ##
    # Adds text to the current element.
    #
    # @param data A string.  This should be either an 8-bit string
    #    containing ASCII text, or a Unicode string.

    def data(self, data):
        self._data.append(data)

    ##
    # Opens a new element.
    #
    # @param tag The element name.
    # @param attrib A dictionary containing element attributes.
    # @return The opened element.
    # @defreturn Element

    def start(self, tag, attrs):
        self._flush()
        self._last = elem = self._factory(tag, attrs)
        if self._elem:
            self._elem[-1].append(elem)
        self._elem.append(elem)
        self._tail = 0
        return elem

    ##
    # Closes the current element.
    #
    # @param tag The element name.
    # @return The closed element.
    # @defreturn Element

    def end(self, tag):
        self._flush()
        self._last = self._elem.pop()
        assert self._last.tag == tag,\
               "end tag mismatch (expected %s, got %s)" % (
                   self._last.tag, tag)
        self._tail = 1
        return self._last

##
# Element structure builder for XML source data, based on the
# <b>expat</b> parser.
#
# @keyparam target Target object.  If omitted, the builder uses an
#     instance of the standard {@link #TreeBuilder} class.
# @keyparam html Predefine HTML entities.  This flag is not supported
#     by the current implementation.
# @keyparam encoding Optional encoding.  If given, the value overrides
#     the encoding specified in the XML file.
# @see #ElementTree
# @see #TreeBuilder

class XMLParser:

    def __init__(self, html=0, target=None, encoding=None):
        try:
            from xml.parsers import expat
        except ImportError:
            try:
                import pyexpat as expat
            except ImportError:
                raise ImportError(
                    "No module named expat; use SimpleXMLTreeBuilder instead"
                    )
        parser = expat.ParserCreate(encoding, "}")
        if target is None:
            target = TreeBuilder()
        # underscored names are provided for compatibility only
        self.parser = self._parser = parser
        self.target = self._target = target
        self._error = expat.error
        self._names = {} # name memo cache
        # main callbacks
        parser.DefaultHandlerExpand = self._default
        if hasattr(target, 'start'):
            parser.StartElementHandler = self._start
        if hasattr(target, 'end'):
            parser.EndElementHandler = self._end
        if hasattr(target, 'data'):
            parser.CharacterDataHandler = target.data
        # miscellaneous callbacks
        if hasattr(target, 'comment'):
            parser.CommentHandler = target.comment
        if hasattr(target, 'pi'):
            parser.ProcessingInstructionHandler = target.pi
        # let expat do the buffering, if supported
        try:
            parser.buffer_text = 1
        except AttributeError:
            pass
        # use new-style attribute handling, if supported
        try:
            parser.ordered_attributes = 1
            parser.specified_attributes = 1
            if hasattr(target, 'start'):
                parser.StartElementHandler = self._start_list
        except AttributeError:
            pass
        self._doctype = None
        self.entity = {}
        try:
            self.version = "Expat %d.%d.%d" % expat.version_info
        except AttributeError:
            pass # unknown

    def _raiseerror(self, value):
        err = ParseError(value)
        err.code = value.code
        err.position = value.lineno, value.offset
        raise err

    def _fixname(self, key):
        # expand qname, and convert name string to ascii, if possible
        try:
            name = self._names[key]
        except KeyError:
            name = key
            if "}" in name:
                name = "{" + name
            self._names[key] = name
        return name

    def _start(self, tag, attrib_in):
        fixname = self._fixname
        tag = fixname(tag)
        attrib = {}
        for key, value in attrib_in.items():
            attrib[fixname(key)] = value
        return self.target.start(tag, attrib)

    def _start_list(self, tag, attrib_in):
        fixname = self._fixname
        tag = fixname(tag)
        attrib = {}
        if attrib_in:
            for i in range(0, len(attrib_in), 2):
                attrib[fixname(attrib_in[i])] = attrib_in[i+1]
        return self.target.start(tag, attrib)

    def _end(self, tag):
        return self.target.end(self._fixname(tag))

    def _default(self, text):
        prefix = text[:1]
        if prefix == "&":
            # deal with undefined entities
            try:
                data_handler = self.target.data
            except AttributeError:
                return
            try:
                data_handler(self.entity[text[1:-1]])
            except KeyError:
                from xml.parsers import expat
                err = expat.error(
                    "undefined entity %s: line %d, column %d" %
                    (text, self.parser.ErrorLineNumber,
                    self.parser.ErrorColumnNumber)
                    )
                err.code = 11 # XML_ERROR_UNDEFINED_ENTITY
                err.lineno = self.parser.ErrorLineNumber
                err.offset = self.parser.ErrorColumnNumber
                raise err
        elif prefix == "<" and text[:9] == "<!DOCTYPE":
            self._doctype = [] # inside a doctype declaration
        elif self._doctype is not None:
            # parse doctype contents
            if prefix == ">":
                self._doctype = None
                return
            text = text.strip()
            if not text:
                return
            self._doctype.append(text)
            n = len(self._doctype)
            if n > 2:
                type = self._doctype[1]
                if type == "PUBLIC" and n == 4:
                    name, type, pubid, system = self._doctype
                    if pubid:
                        pubid = pubid[1:-1]
                elif type == "SYSTEM" and n == 3:
                    name, type, system = self._doctype
                    pubid = None
                else:
                    return
                if hasattr(self.target, "doctype"):
                    self.target.doctype(name, pubid, system[1:-1])
                elif self.doctype != self._XMLParser__doctype:
                    # warn about deprecated call
                    self._XMLParser__doctype(name, pubid, system[1:-1])
                    self.doctype(name, pubid, system[1:-1])
                self._doctype = None

    ##
    # (Deprecated) Handles a doctype declaration.
    #
    # @param name Doctype name.
    # @param pubid Public identifier.
    # @param system System identifier.

    def doctype(self, name, pubid, system):
        """This method of XMLParser is deprecated."""
        warnings.warn(
            "This method of XMLParser is deprecated.  Define doctype() "
            "method on the TreeBuilder target.",
            DeprecationWarning,
            )

    # sentinel, if doctype is redefined in a subclass
    __doctype = doctype

    ##
    # Feeds data to the parser.
    #
    # @param data Encoded data.

    def feed(self, data):
        try:
            self.parser.Parse(data, 0)
        except self._error as v:
            self._raiseerror(v)

    ##
    # Finishes feeding data to the parser.
    #
    # @return An element structure.
    # @defreturn Element

    def close(self):
        try:
            self.parser.Parse("", 1) # end of data
        except self._error as v:
            self._raiseerror(v)
        try:
            close_handler = self.target.close
        except AttributeError:
            pass
        else:
            return close_handler()
        finally:
            # get rid of circular references
            del self.parser, self._parser
            del self.target, self._target


# Import the C accelerators
try:
    # Element, SubElement, ParseError, TreeBuilder, XMLParser
    from _elementtree import *
except ImportError:
    pass
else:
    # Overwrite 'ElementTree.parse' and 'iterparse' to use the C XMLParser

    class ElementTree(ElementTree):
        def parse(self, source, parser=None):
            close_source = False
            if not hasattr(source, 'read'):
                source = open(source, 'rb')
                close_source = True
            try:
                if parser is not None:
                    while True:
                        data = source.read(65536)
                        if not data:
                            break
                        parser.feed(data)
                    self._root = parser.close()
                else:
                    parser = XMLParser()
                    self._root = parser._parse(source)
                return self._root
            finally:
                if close_source:
                    source.close()

    class iterparse:
        """Parses an XML section into an element tree incrementally.

        Reports what’s going on to the user. 'source' is a filename or file
        object containing XML data. 'events' is a list of events to report back.
        The supported events are the strings "start", "end", "start-ns" and
        "end-ns" (the "ns" events are used to get detailed namespace
        information). If 'events' is omitted, only "end" events are reported.
        'parser' is an optional parser instance. If not given, the standard
        XMLParser parser is used. Returns an iterator providing
        (event, elem) pairs.
        """

        root = None
        def __init__(self, file, events=None, parser=None):
            self._close_file = False
            if not hasattr(file, 'read'):
                file = open(file, 'rb')
                self._close_file = True
            self._file = file
            self._events = []
            self._index = 0
            self._error = None
            self.root = self._root = None
            if parser is None:
                parser = XMLParser(target=TreeBuilder())
            self._parser = parser
            self._parser._setevents(self._events, events)

        def __next__(self):
            while True:
                try:
                    item = self._events[self._index]
                    self._index += 1
                    return item
                except IndexError:
                    pass
                if self._error:
                    e = self._error
                    self._error = None
                    raise e
                if self._parser is None:
                    self.root = self._root
                    if self._close_file:
                        self._file.close()
                    raise StopIteration
                # load event buffer
                del self._events[:]
                self._index = 0
                data = self._file.read(16384)
                if data:
                    try:
                        self._parser.feed(data)
                    except SyntaxError as exc:
                        self._error = exc
                else:
                    self._root = self._parser.close()
                    self._parser = None

        def __iter__(self):
            return self

# compatibility
XMLTreeBuilder = XMLParser

# workaround circular import.
try:
    from ElementC14N import _serialize_c14n
    _serialize["c14n"] = _serialize_c14n
except ImportError:
    pass