Categories: S60 | Python | How To | Code Examples | XML

From Forum Nokia Wiki

It is possible to store settings in XML files.

This library uses cElementTree. Since PyS60 1.3.22 it is much faster to load the library! So I advice to upgrade your PyS60 installation if you haven't done it yet.

The library

# imports.
try:
    from cElementTree import ElementTree, XMLTreeBuilder
except:
    import sys
    sys.exit("cElementTree module is not installed!")
 
import string, urllib, os.path
 
## XML Parser used with the framework.
class MParser( ElementTree ):
    ## The constructor.
    #  @param self The object pointer.
    def __init__( self ):
        ElementTree.__init__( self )
 
    ## Download the xml file at the given url (@a aUrl), read it, create and 
    #  return an xml tree object from the data string.
    #  @param self The object pointer.
    #  @param aUrl xml file url to downloaded and parsed.
    def fromurl( self, aUrl ):
        # urlopen return file object
        ressource = urllib.urlopen( aUrl )
        string = ressource.read( )
        return self.fromstring( string )
 
    ## Create an xml tree object from a string.
    #  @param self The object pointer.
    #  @param aString The string to be parsed by XMLTreeBuilder in order to 
    #  create an xml tree object.
    def fromstring( self, aString ):
        parser = XMLTreeBuilder( )
        parser.feed( aString )
        return parser.close( )
 
    ## Create an xml tree object from a file.
    #  @param self The object pointer.
    #  @param aFilePath The file path to be parsed in order to create an xml 
    #  tree object.
    def fromfile( self, aFilePath ):
        self.parse( aFilePath )
        return self.getroot( )
 
    ## Parse a xml object to its string representation.
    #  @param self The object pointer.
    #  @param aElement Element to be parsed.
    #  @param aEncoding Encoding to use for the string.
    def tostring( self, aElement, aEncoding=None ):
        class dummy:
            pass
        data = []
        file = dummy( )
        file.write = data.append
        ElementTree( aElement ).write( file, aEncoding )
        return string.join( data, "" )
 
 
## Setting class used with the framework.
class Settings( object, MParser ):
    ## The default file schemas to write in the settings file.
    _iDefaultSchemas = """
<?xml version="1.0" encoding="UTF-8"?>
<settings>
    <host>server.xxx</host>
    <port>80</port>
    <imagedir>D:\\AppDirectory\\</imagedir>
</settings>
"""
    ## Key dictionnary containing the settings options.
    _iKeys = {}
 
    ## file header.
    _iFileHeader = u'<?xml version="1.0" encoding="UTF-8"?>'
 
    ## Parent tag key.
    _iRootTag = u'settings'
 
    ## The constructor.
    #  @param self The object pointer.
    #  @param aFile A settings file path.
    #  @param aSchemas If given, XML to write in the settings file if empty and
    #  or has to be created.
    def __init__( self, aFile, aSchemas=None ):
        if os.path.splitext( aFile )[1].lower( ) != ".xml":
            sys.exit( "XML files expected" )
 
        ## File path.
        self._iFile = aFile
        # set default structure if given.
        if aSchemas:
            self._iDefaultSchemas = aSchemas
        # get the last config from the file.
        self._readSettings( )
 
 
    ## Set a new option on the settings file.
    #  @param self The object pointer.
    #  @param aOption New option to add.
    #  @param aValue Value to set for the option.
    def set( self, aOption, aValue ):
        # set the given key.
        self._iKeys[aOption] = aValue
        # write in the settings file.
        self._writeSettings( )
 
    ## Get options on the settings file.
    #  @param self The object pointer.
    #  @param aOption If an option is given, the method will return its value
    #  or None if it doesn't exist. If no options given, the method returns the
    #  entire dictionnary.
    def get( self, aOption=None ):
        try:
            if aOption:
                return self._iKeys[aOption]
            else:
                return self._iKeys
        except:
            return None
    
    ## Set a new option on the settings file.
    #  @param self The object pointer.
    #  @param aOption Key to remove.
    def remove( self, aOption ):
        # set the given key.
        del self._iKeys[aOption]
        # write in the settings file.
        self._writeSettings( )
 
    ## Read the settings from the settings file.
    #  @param self The object pointer.
    def _readSettings( self ):
        # needed variable.
        root = None
 
        # next node.
        def nextNode( aParent ):
            elements = {}
            dict = None
            for node in parent:
             if len(node) != 0:
                 tag, dict = next_node( node )
                 elements[tag] = dict
             else:
                 elements[node.tag] = node.text
            return parent.tag, elements
 
        # if the file exists, we read it.
        if os.path.isfile( self._iFile ) and os.path.exists( self._iFile ):
            root = self.fromfile( self._iFile )
        # if not we create it and write _iDefaultSchemas inside.
        else:
            rs = open( self._iFile, 'w' )
            rs.writelines( self._iDefaultSchemas.strip( ) )
            rs.close( )
            root = self.fromstring( self._iDefaultSchemas.strip( ) )
 
        for node in root:
            if len( node ) != 0:
                tag, dict = nextNode( node )
                self._iKeys[tag] = dict
            else:
                self._iKeys[node.tag] = node.text
 
 
 
    ## Write the settings into the settings file.
    #  @param self The object pointer.
    def _writeSettings( self ):
        rs = open( self._iFile, 'w' )
        rs.write( self._iFileHeader+'\n' )
        rs.write( u'<'+self._iRootTag+'>'+'\n' )
        for key in self._iKeys:
            if self._iKeys[key]:
                rs.write( "    <"+key+">"+self._iKeys[key]+"</"+key+">"+'\n' )
            else:
                rs.write( "    <"+key+"></"+key+">"+'\n' )
 
        rs.write( u'</'+self._iRootTag+'>'+'\n' )
        rs.close( )

Usage

# creates test.xml in the memory drive.
config = Settings( "E:\\Others\\test.xml" )
 
# print all key.
print config.get()
 
# set some key.
config.set('uid', 'blablabla')
config.set('uname', 'LFDM')
 
# print all key.
print config.get()
    
# print only uid.
print 'uid is: ', config.get('uid')
    
# remove uname key.
config.remove('uname')
    
# print all keys.
print config.get()