Module xml_preferences

xml_preferences uses a scheme to create a hierarchy of objects that represent the data stored in an XML files. CHanges to the objects can later to saved back into an XML file.

The inspiration for this module is to store preferences for applications.

Classes

class xml_preferences.XmlPreferences

__init__( scheme )

The scheme is an instance of xml_preferences.Scheme.

load( filename )

Reads the preferences from the filename and returns the resulting tree of xml_preferences.PreferencesNode objects.

In case of an error xml_preferences.ParseError is raise.

loadString( text )

Reads the preferences from the string text and returns the resulting tree of xml_preferences.PreferencesNode objects.

In case of an error xml_preferences.ParseError is raise.

save( data_node )

Write the xml_preferences.PreferencesNode data_node hierarchy into the file used to load() the preferences.

saveAs( data_node, filename )

Write the xml_preferences.PreferencesNode data_node hierarchy into fileaname.

saveToString( data_node )

Write the xml_preferences.PreferencesNode data_node hierarchy into a string and return the string.

saveToFile( data_node, f )

Write the xml_preferences.PreferencesNode data_node hierarchy into the file object f.

class xml_preferences.Scheme

__init__( document_root )

The document_root is an instance of xml_preferences.SchemeNode and represent the top level XML document element.

dumpScheme( f )

Write a dump of the scheme into the file object f.

This is useful for debugging issues with scheme design.

class xml_preferences.SchemeNode

__init__( factory, element_name, all_attribute_info=None, element_plurality=False, key_attribute=None, collection_name=None, store_as=None, default=True, default_attributes=None )

The SchemeNode represents on XML element with the name element_name.

Any attributes that element has are listed in all_attribute_info, which is a tuple/list of names or name,type pairs. For example:

all_attribute_info=(‘description’, (‘count’, int))

The SchemeNode can represent an in three ways:

1. The element will only appear once.

2. The element has element_plurality set to True and can appear many times and will be stored as a list of elements in its parent.

3. The element has a key_attribute and can appear many times and will be stored as a dictionary in its parent.

The collection_name defaults to the element_name. The collection_name is passed to the parent setChildNodeList or setChildNodeMap functions.

store_as defaults to the element_name and is used to name the python variable that this node is store in its in parent object.

When default is True and there is not XML that matches this SchemeNode a default value will be stored in the parent object.

When the node is defaulted the attributes of the node can be set from a dictionary pass as default_attributes.

dumpScheme( f, indent=0 )

Write a dump of the scheme into the file object f.

This is useful for debugging issues with scheme design.

addSchemeChild( scheme_node ) __lshift__( scheme_node )

Add scheme_node as a child element of this SchemeNode. The << operator is useful in making the scheme definition readable.

class xml_preferences.PreferencesNode

For typical use all the set and get functions provide all the necessary features. That can be overriden to create special behaviour. It is assumed that all attribures are initised to a suitable value in __init__.

__init__()

Derive from PreferencesNode to initialise the variables used to hold the parsed XML preferences.

finaliseNode( self )

Called after all attributes and child nodes have been set on this node.

Use this call to default any missing preferences.

setAttr( self, name, value )

Called to save the value of an attribute. The default implemention is:

setattr( self, name, value )

setChildNode( self, name, node )

Called to save the value of singleton child element. The default implemention is:

setattr( self, name, node )

setChildNodeList( self, collection_name, node )

Called to save the value of the next element to added to a list. The default implemention is:

getattr( self, collection_name ).append( node )

setChildNodeMap( self, collection_name, key, node )

Called to save the value of the next element into a dict using the key. The default implemention is:

getattr( self, collection_name )[ key ] = node

getAttr( self, name )

Called to get the value of the name attribute. The default implemention is:

return getattr( self, name )

getChildNode( self, name )

Called to get the value of the name child node. The default implemention is:

return getattr( self, name )

getChildNodeList( self, collection_name )

Called to get a list of values of the collection_name child nodes, which are assumed to be stored in a list. The default implemention is:

return getattr( self, name )

getChildNodeMap( self, collection_name )

Called to get a list value of the collection_name child nodes, which are assumed to be stored in a dict. The default implemention is:

return getattr( self, name ).values()

dumpNode( self, f, indent=0 )

Write a dump of the PreferencesNode hierarchy into file object f.

Set indent to the number of spaces to indent the dumped text.

Useful when debugging.

Example

See test_xml_preferences.py for example use.