xml2dict.py

# -*- coding: utf-8 -*-

try:
    from defusedexpat import pyexpat as expat
except ImportError:
    from xml.parsers import expat
from xml.sax.saxutils import XMLGenerator
from xml.sax.xmlreader import AttributesImpl
try:  # pragma no cover
    from cStringIO import StringIO
except ImportError:  # pragma no cover
    try:
        from StringIO import StringIO
    except ImportError:
        from io import StringIO
try:  # pragma no cover
    from collections import OrderedDict
except ImportError:  # pragma no cover
    try:
        from ordereddict import OrderedDict
    except ImportError:
        OrderedDict = dict


__author__ = 'Martin Blech'
__version__ = '0.11.0'
__license__ = 'MIT'


class ParsingInterrupted(Exception):
    pass


class _DictSAXHandler(object):
    def __init__(self,
                 item_depth=0,
                 item_callback=lambda *args: True,
                 xml_attribs=True,
                 attr_prefix='@',
                 cdata_key='#text',
                 force_cdata=False,
                 cdata_separator='',
                 postprocessor=None,
                 dict_constructor=OrderedDict,
                 strip_whitespace=True,
                 namespace_separator=':',
                 namespaces=None,
                 force_list=None):
        self.path = []
        self.stack = []
        self.data = []
        self.item = None
        self.item_depth = item_depth
        self.xml_attribs = xml_attribs
        self.item_callback = item_callback
        self.attr_prefix = attr_prefix
        self.cdata_key = cdata_key
        self.force_cdata = force_cdata
        self.cdata_separator = cdata_separator
        self.postprocessor = postprocessor
        self.dict_constructor = dict_constructor
        self.strip_whitespace = strip_whitespace
        self.namespace_separator = namespace_separator
        self.namespaces = namespaces
        self.namespace_declarations = OrderedDict()
        self.force_list = force_list

    def _build_name(self, full_name):
        if not self.namespaces:
            return full_name
        i = full_name.rfind(self.namespace_separator)
        if i == -1:
            return full_name
        namespace, name = full_name[:i], full_name[i+1:]
        short_namespace = self.namespaces.get(namespace, namespace)
        if not short_namespace:
            return name
        else:
            return self.namespace_separator.join((short_namespace, name))

    def _attrs_to_dict(self, attrs):
        if isinstance(attrs, dict):
            return attrs
        return self.dict_constructor(zip(attrs[0::2], attrs[1::2]))

    def startNamespaceDecl(self, prefix, uri):
        self.namespace_declarations[prefix or ''] = uri

    def startElement(self, full_name, attrs):
        name = self._build_name(full_name)
        attrs = self._attrs_to_dict(attrs)
        if attrs and self.namespace_declarations:
            attrs['xmlns'] = self.namespace_declarations
            self.namespace_declarations = OrderedDict()
        self.path.append((name, attrs or None))
        if len(self.path) > self.item_depth:
            self.stack.append((self.item, self.data))
            if self.xml_attribs:
                attr_entries = []
                for key, value in attrs.items():
                    key = self.attr_prefix+self._build_name(key)
                    if self.postprocessor:
                        entry = self.postprocessor(self.path, key, value)
                    else:
                        entry = (key, value)
                    if entry:
                        attr_entries.append(entry)
                attrs = self.dict_constructor(attr_entries)
            else:
                attrs = None
            self.item = attrs or None
            self.data = []

    def endElement(self, full_name):
        name = self._build_name(full_name)
        if len(self.path) == self.item_depth:
            item = self.item
            if item is None:
                item = (None if not self.data
                        else self.cdata_separator.join(self.data))

            should_continue = self.item_callback(self.path, item)
            if not should_continue:
                raise ParsingInterrupted()
        if len(self.stack):
            data = (None if not self.data
                    else self.cdata_separator.join(self.data))
            item = self.item
            self.item, self.data = self.stack.pop()
            if self.strip_whitespace and data:
                data = data.strip() or None
            if data and self.force_cdata and item is None:
                item = self.dict_constructor()
            if item is not None:
                if data:
                    self.push_data(item, self.cdata_key, data)
                self.item = self.push_data(self.item, name, item)
            else:
                self.item = self.push_data(self.item, name, data)
        else:
            self.item = None
            self.data = []
        self.path.pop()

    def characters(self, data):
        if not self.data:
            self.data = [data]
        else:
            self.data.append(data)

    def push_data(self, item, key, data):
        if self.postprocessor is not None:
            result = self.postprocessor(self.path, key, data)
            if result is None:
                return item
            key, data = result
        if item is None:
            item = self.dict_constructor()
        try:
            value = item[key]
            if isinstance(value, list):
                value.append(data)
            else:
                item[key] = [value, data]
        except KeyError:
            if self._should_force_list(key, data):
                item[key] = [data]
            else:
                item[key] = data
        return item

    def _should_force_list(self, key, value):
        if not self.force_list:
            return False
        try:
            return key in self.force_list
        except TypeError:
            return self.force_list(self.path[:-1], key, value)


def parse(xml_input, encoding=None, expat=expat, process_namespaces=False,
          namespace_separator=':', disable_entities=True, **kwargs):
    """Parse the given XML input and convert it into a dictionary.
    `xml_input` can either be a `string` or a file-like object.
    If `xml_attribs` is `True`, element attributes are put in the dictionary
    among regular child elements, using `@` as a prefix to avoid collisions. If
    set to `False`, they are just ignored.
    Simple example::
        [u'1', u'2']
    If `item_depth` is `0`, the function returns a dictionary for the root
    element (default behavior). Otherwise, it calls `item_callback` every time
    an item at the specified depth is found and returns `None` in the end
    (streaming mode).
    The callback function receives two parameters: the `path` from the document
    root to the item (name-attribs pairs), and the `item` (dict). If the
    callback's return value is false-ish, parsing will be stopped with the
    :class:`ParsingInterrupted` exception.
    Streaming example::

        path:[(u'a', {u'prop': u'x'}), (u'b', None)] item:1
        path:[(u'a', {u'prop': u'x'}), (u'b', None)] item:2
    The optional argument `postprocessor` is a function that takes `path`,
    `key` and `value` as positional arguments and returns a new `(key, value)`
    pair where both `key` and `value` may have changed. Usage example::

        OrderedDict([(u'a', OrderedDict([(u'b:int', [1, 2]), (u'b', u'x')]))])
    You can pass an alternate version of `expat` (such as `defusedexpat`) by
    using the `expat` parameter. E.g:

        OrderedDict([(u'a', u'hello')])
    You can use the force_list argument to force lists to be created even
    when there is only a single child of a given level of hierarchy. The
    force_list argument is a tuple of keys. If the key for a given level
    of hierarchy is in the force_list argument, that level of hierarchy
    will have a list as a child (even if there is only one sub-element).
    The index_keys operation takes precendence over this. This is applied
    after any user-supplied postprocessor has already run.
        For example, given this input:
        <servers>
          <server>
            <name>host1</name>
            <os>Linux</os>
            <interfaces>
              <interface>
                <name>em0</name>
                <ip_address>10.0.0.1</ip_address>
              </interface>
            </interfaces>
          </server>
        </servers>
        If called with force_list=('interface',), it will produce
        this dictionary:
        {'servers':
          {'server':
            {'name': 'host1',
             'os': 'Linux'},
             'interfaces':
              {'interface':
                [ {'name': 'em0', 'ip_address': '10.0.0.1' } ] } } }
        `force_list` can also be a callable that receives `path`, `key` and
        `value`. This is helpful in cases where the logic that decides whether
        a list should be forced is more complex.
    """
    handler = _DictSAXHandler(namespace_separator=namespace_separator,
                              **kwargs)
    if isinstance(xml_input, str):
        if not encoding:
            encoding = 'utf-8'
        xml_input = xml_input.encode(encoding)
    if not process_namespaces:
        namespace_separator = None
    parser = expat.ParserCreate(
        encoding,
        namespace_separator
    )
    try:
        parser.ordered_attributes = True
    except AttributeError:
        # Jython's expat does not support ordered_attributes
        pass
    parser.StartNamespaceDeclHandler = handler.startNamespaceDecl
    parser.StartElementHandler = handler.startElement
    parser.EndElementHandler = handler.endElement
    parser.CharacterDataHandler = handler.characters
    parser.buffer_text = True
    if disable_entities:
        try:
            # Attempt to disable DTD in Jython's expat parser (Xerces-J).
            feature = "http://apache.org/xml/features/disallow-doctype-decl"
            parser._reader.setFeature(feature, True)
        except AttributeError:
            # For CPython / expat parser.
            # Anything not handled ends up here and entities aren't expanded.
            parser.DefaultHandler = lambda x: None
            # Expects an integer return; zero means failure -> expat.ExpatError.
            parser.ExternalEntityRefHandler = lambda *x: 1
    if hasattr(xml_input, 'read'):
        parser.ParseFile(xml_input)
    else:
        parser.Parse(xml_input, True)
    return handler.item


def _process_namespace(name, namespaces, ns_sep=':', attr_prefix='@'):
    if not namespaces:
        return name
    try:
        ns, name = name.rsplit(ns_sep, 1)
    except ValueError:
        pass
    else:
        ns_res = namespaces.get(ns.strip(attr_prefix))
        name = '{0}{1}{2}{3}'.format(
            attr_prefix if ns.startswith(attr_prefix) else '',
            ns_res, ns_sep, name) if ns_res else name
    return name


def _emit(key, value, content_handler,
          attr_prefix='@',
          cdata_key='#text',
          depth=0,
          preprocessor=None,
          pretty=False,
          newl='\n',
          indent='\t',
          namespace_separator=':',
          namespaces=None,
          full_document=True):
    key = _process_namespace(key, namespaces, namespace_separator, attr_prefix)
    if preprocessor is not None:
        result = preprocessor(key, value)
        if result is None:
            return
        key, value = result
    if (not hasattr(value, '__iter__')
            or isinstance(value, str)
            or isinstance(value, dict)):
        value = [value]
    for index, v in enumerate(value):
        if full_document and depth == 0 and index > 0:
            raise ValueError('document with multiple roots')
        if v is None:
            v = OrderedDict()
        elif not isinstance(v, dict):
            v = str(v)
        if isinstance(v, str):
            v = OrderedDict(((cdata_key, v),))
        cdata = None
        attrs = OrderedDict()
        children = []
        for ik, iv in v.items():
            if ik == cdata_key:
                cdata = iv
                continue
            if ik.startswith(attr_prefix):
                ik = _process_namespace(ik, namespaces, namespace_separator,
                                        attr_prefix)
                if ik == '@xmlns' and isinstance(iv, dict):
                    for k, v in iv.items():
                        attr = 'xmlns{0}'.format(':{0}'.format(k) if k else '')
                        attrs[attr] = str(v)
                    continue
                if not isinstance(iv, str):
                    iv = str(iv)
                attrs[ik[len(attr_prefix):]] = iv
                continue
            children.append((ik, iv))
        if pretty:
            content_handler.ignorableWhitespace(depth * indent)
        content_handler.startElement(key, AttributesImpl(attrs))
        if pretty and children:
            content_handler.ignorableWhitespace(newl)
        for child_key, child_value in children:
            _emit(child_key, child_value, content_handler,
                  attr_prefix, cdata_key, depth+1, preprocessor,
                  pretty, newl, indent, namespaces=namespaces,
                  namespace_separator=namespace_separator)
        if cdata is not None:
            content_handler.characters(cdata)
        if pretty and children:
            content_handler.ignorableWhitespace(depth * indent)
        content_handler.endElement(key)
        if pretty and depth:
            content_handler.ignorableWhitespace(newl)


def unparse(input_dict, output=None, encoding='utf-8', full_document=True,
            short_empty_elements=False,
            **kwargs):
    """Emit an XML document for the given `input_dict` (reverse of `parse`).
    The resulting XML document is returned as a string, but if `output` (a
    file-like object) is specified, it is written there instead.
    Dictionary keys prefixed with `attr_prefix` (default=`'@'`) are interpreted
    as XML node attributes, whereas keys equal to `cdata_key`
    (default=`'#text'`) are treated as character data.
    The `pretty` parameter (default=`False`) enables pretty-printing. In this
    mode, lines are terminated with `'\n'` and indented with `'\t'`, but this
    can be customized with the `newl` and `indent` parameters.
    """
    if full_document and len(input_dict) != 1:
        raise ValueError('Document must have exactly one root.')
    must_return = False
    if output is None:
        output = StringIO()
        must_return = True
    if short_empty_elements:
        content_handler = XMLGenerator(output, encoding, True)
    else:
        content_handler = XMLGenerator(output, encoding)
    if full_document:
        content_handler.startDocument()
    for key, value in input_dict.items():
        _emit(key, value, content_handler, full_document=full_document,
              **kwargs)
    if full_document:
        content_handler.endDocument()
    if must_return:
        value = output.getvalue()
        try:  # pragma no cover
            value = value.decode(encoding)
        except AttributeError:  # pragma no cover
            pass
        return value

if __name__ == '__main__':  # pragma: no cover
    import sys
    import marshal
    try:
        stdin = sys.stdin.buffer
        stdout = sys.stdout.buffer
    except AttributeError:
        stdin = sys.stdin
        stdout = sys.stdout

    (item_depth,) = sys.argv[1:]
    item_depth = int(item_depth)


    def handle_item(path, item):
        marshal.dump((path, item), stdout)
        return True

    try:
        root = parse(stdin,
                     item_depth=item_depth,
                     item_callback=handle_item,
                     dict_constructor=dict)
        if item_depth == 0:
            handle_item([], root)
    except KeyboardInterrupt:
        pass