xmltodict.py

#!/usr/bin/env python
"Makes working with XML feel like you are working with JSON"

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

try: # pragma no cover
    _basestring = basestring
except NameError: # pragma no cover
    _basestring = str
try: # pragma no cover
    _unicode = unicode
except NameError: # pragma no cover
    _unicode = str

__author__ = 'Martin Blech'
__version__ = '0.7.0'
__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):
        self.path = []
        self.stack = []
        self.data = None
        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

    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 startElement(self, full_name, attrs):
        name = self._build_name(full_name)
        attrs = self.dict_constructor(zip(attrs[0::2], attrs[1::2]))
        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:
                attrs = self.dict_constructor(
                    (self.attr_prefix+key, value)
                    for (key, value) in attrs.items())
            else:
                attrs = None
            self.item = attrs or None
            self.data = None

    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 = self.data
            should_continue = self.item_callback(self.path, item)
            if not should_continue:
                raise ParsingInterrupted()
        if len(self.stack):
            item, data = self.item, self.data
            self.item, self.data = self.stack.pop()
            if self.strip_whitespace and data is not None:
                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 = self.data = None
        self.path.pop()

    def characters(self, data):
        if not self.data:
            self.data = data
        else:
            self.data += self.cdata_separator + 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:
            item[key] = data
        return item

def parse(xml_input, encoding='utf-8', expat=expat, process_namespaces=False,
          namespace_separator=':', **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::

        >>> doc = xmltodict.parse(\"\"\"
        ... <a prop="x">
        ...   <b>1</b>
        ...   <b>2</b>
        ... </a>
        ... \"\"\")
        >>> doc['a']['@prop']
        u'x'
        >>> doc['a']['b']
        [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::

        >>> def handle(path, item):
        ...     print 'path:%s item:%s' % (path, item)
        ...     return True
        ...
        >>> xmltodict.parse(\"\"\"
        ... <a prop="x">
        ...   <b>1</b>
        ...   <b>2</b>
        ... </a>\"\"\", item_depth=2, item_callback=handle)
        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::

        >>> def postprocessor(path, key, value):
        ...     try:
        ...         return key + ':int', int(value)
        ...     except (ValueError, TypeError):
        ...         return key, value
        >>> xmltodict.parse('<a><b>1</b><b>2</b><b>x</b></a>',
        ...                 postprocessor=postprocessor)
        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:

        >>> import defusedexpat
        >>> xmltodict.parse('<a>hello</a>', expat=defusedexpat.pyexpat)
        OrderedDict([(u'a', u'hello')])

    """
    handler = _DictSAXHandler(namespace_separator=namespace_separator, **kwargs)
    parser = expat.ParserCreate(
        encoding,
        namespace_separator if process_namespaces else None
    )
    parser.ordered_attributes = True
    parser.StartElementHandler = handler.startElement
    parser.EndElementHandler = handler.endElement
    parser.CharacterDataHandler = handler.characters
    try:
        parser.ParseFile(xml_input)
    except (TypeError, AttributeError):
        if isinstance(xml_input, _unicode):
            xml_input = xml_input.encode(encoding)
        parser.Parse(xml_input, True)
    return handler.item

def _emit(key, value, content_handler,
          attr_prefix='@',
          cdata_key='#text',
          depth=0,
          preprocessor=None,
          pretty=False,
          newl='\n',
          indent='\t'):
    if preprocessor is not None:
        result = preprocessor(key, value)
        if result is None:
            return
        key, value = result
    if not isinstance(value, (list, tuple)):
        value = [value]
    if depth == 0 and len(value) > 1:
        raise ValueError('document with multiple roots')
    for v in value:
        if v is None:
            v = OrderedDict()
        elif not isinstance(v, dict):
            v = _unicode(v)
        if isinstance(v, _basestring):
            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):
                attrs[ik[len(attr_prefix):]] = iv
                continue
            children.append((ik, iv))
        if pretty and depth:
            content_handler.ignorableWhitespace(newl + indent * depth)
        content_handler.startElement(key, AttributesImpl(attrs))
        for child_key, child_value in children:
            _emit(child_key, child_value, content_handler,
                  attr_prefix, cdata_key, depth+1, preprocessor,
                  pretty, newl, indent)
        if cdata is not None:
            content_handler.characters(cdata)
        content_handler.endElement(key)
        if pretty and depth:
            content_handler.ignorableWhitespace(newl + indent * (depth - 1))

def unparse(input_dict, output=None, encoding='utf-8', **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.

    """
    ((key, value),) = input_dict.items()
    must_return = False
    if output == None:
        output = StringIO()
        must_return = True
    content_handler = XMLGenerator(output, encoding)
    content_handler.startDocument()
    _emit(key, value, content_handler, **kwargs)
    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

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

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

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