ParseXML.py

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"""
Copyright 2008 Free Software Foundation, Inc.
This file is part of GNU Radio

GNU Radio Companion is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

GNU Radio Companion is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
"""
##@package grc.gui.ParseXML
#Parse xml files to nested data and vice-versa.
#@author Josh Blum

from lxml import etree
from Utils import odict

XMLSyntaxError = etree.XMLSyntaxError

def validate_dtd(xml_file, dtd_file=None):
        """!
        Validate an xml file against its dtd.
        @param xml_file the xml file
        @param dtd_file the optional dtd file
        @throws Exception validation fails
        """
        if dtd_file:
                dtd = etree.DTD(dtd_file)
                xml = etree.parse(xml_file)
                if not dtd.validate(xml.getroot()):
                        raise XMLSyntaxError, '\n'.join(map(str, dtd.error_log.filter_from_errors()))
        else:
                parser = etree.XMLParser(dtd_validation=True)
                xml = etree.parse(xml_file, parser=parser)
                if parser.error_log:
                        raise XMLSyntaxError, '\n'.join(map(str, parser.error_log.filter_from_errors()))

def from_file(xml_file):
        """!
        Create nested data from an xml file using the from xml helper.
        @param xml_file the xml file path
        @return the nested data
        """
        xml = etree.parse(xml_file).getroot()
        return _from_file(xml)

def _from_file(xml):
        """!
        Recursivly parse the xml tree into nested data format.
        @param xml the xml tree
        @return the nested data
        """
        tag = xml.tag
        if not len(xml):
                return odict({tag: xml.text or ''}) #store empty tags (text is None) as empty string
        nested_data = odict()
        for elem in xml:
                key, value = _from_file(elem).items()[0]
                if nested_data.has_key(key): nested_data[key].append(value)
                else: nested_data[key] = [value]
        #delistify if the length of values is 1
        for key, values in nested_data.iteritems():
                if len(values) == 1: nested_data[key] = values[0]
        return odict({tag: nested_data})

def to_file(nested_data, xml_file):
        """!
        Write an xml file and use the to xml helper method to load it.
        @param nested_data the nested data
        @param xml_file the xml file path
        """
        xml = _to_file(nested_data)[0]
        open(xml_file, 'w').write(etree.tostring(xml, xml_declaration=True, pretty_print=True))

def _to_file(nested_data):
        """!
        Recursivly parse the nested data into xml tree format.
        @param nested_data the nested data
        @return the xml tree filled with child nodes
        """
        nodes = list()
        for key, values in nested_data.iteritems():
                #listify the values if not a list
                if not isinstance(values, (list, set, tuple)):
                        values = [values]
                for value in values:
                        node = etree.Element(key)
                        if isinstance(value, (str, unicode)): node.text = value
                        else: node.extend(_to_file(value))
                        nodes.append(node)
        return nodes

if __name__ == '__main__':
        """Use the main method to test parse xml's functions."""
        pass

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