composite.py

"""
A class which defines a composite object which can store
hieararchical dictionaries with names.

This class is same as a hiearchical dictionary, but it
provides methods to add/access/modify children by name, 
like a Composite.

Created Anand B Pillai <abpillai@gmail.com>

"""
__author__ = "Anand B Pillai"
__maintainer__ = "Anand B Pillai"
__version__ = "0.2"


def normalize(val):
 """ Normalize a string so that it can be used as an attribute
 to a Python object """
 
 if val.find('-') != -1:
 val = val.replace('-','_')

 return val

def denormalize(val):
 """ De-normalize a string """
 
 if val.find('_') != -1:
 val = val.replace('_','-')

 return val

class SpecialDict(dict):
 """ A dictionary type which allows direct attribute
 access to its keys """

 def __getattr__(self, name):

 if name in self.__dict__:
 return self.__dict__[name]
 elif name in self:
 return self.get(name)
 else:
 # Check for denormalized name
 name = denormalize(name)
 if name in self:
 return self.get(name)
 else:
 raise AttributeError('no attribute named %s' % name)

 def __setattr__(self, name, value):

 if name in self.__dict__:
 self.__dict__[name] = value
 elif name in self:
 self[name] = value
 else:
 # Check for denormalized name
 name2 = denormalize(name)
 if name2 in self:
 self[name2] = value
 else:
 # New attribute
 self[name] = value
 
class CompositeDict(SpecialDict):
 """ A class which works like a hierarchical dictionary.
 This class is based on the Composite design-pattern """
 
 ID = 0
 
 def __init__(self, name=''):

 if name:
 self._name = name
 else:
 self._name = ''.join(('id#',str(self.__class__.ID)))
 self.__class__.ID += 1
 
 self._children = []
 # Link back to father
 self._father = None
 self[self._name] = SpecialDict()

 def __getattr__(self, name):

 if name in self.__dict__:
 return self.__dict__[name]
 elif name in self:
 return self.get(name)
 else:
 # Check for denormalized name
 name = denormalize(name)
 if name in self:
 return self.get(name)
 else:
 # Look in children list
 child = self.findChild(name)
 if child:
 return child
 else:
 attr = getattr(self[self._name], name)
 if attr: return attr
 
 raise AttributeError('no attribute named %s' % name)

 def isRoot(self):
 """ Return whether I am a root component or not """

 # If I don't have a parent, I am root
 return not self._father
 
 def isLeaf(self):
 """ Return whether I am a leaf component or not """

 # I am a leaf if I have no children
 return not self._children

 def getName(self):
 """ Return the name of this ConfigInfo object """

 return self._name

 def getIndex(self, child):
 """ Return the index of the child ConfigInfo object 'child' """
 
 if child in self._children:
 return self._children.index(child)
 else:
 return -1

 def getDict(self):
 """ Return the contained dictionary """
 
 return self[self._name]

 def getProperty(self, child, key):
 """ Return the value for the property for child
 'child' with key 'key' """

 # First get the child's dictionary
 childDict = self.getInfoDict(child)
 if childDict:
 return childDict.get(key, None)

 def setProperty(self, child, key, value):
 """ Set the value for the property 'key' for
 the child 'child' to 'value' """

 # First get the child's dictionary
 childDict = self.getInfoDict(child)
 if childDict:
 childDict[key] = value
 
 def getChildren(self):
 """ Return the list of immediate children of this object """
 
 return self._children

 def getAllChildren(self):
 """ Return the list of all children of this object """
 
 l = []
 for child in self._children:
 l.append(child)
 l.extend(child.getAllChildren())
 
 return l

 def getChild(self, name):
 """ Return the immediate child object with the given name """
 
 for child in self._children:
 if child.getName() == name:
 return child

 def findChild(self, name):
 """ Return the child with the given name from the tree """

 # Note - this returns the first child of the given name
 # any other children with similar names down the tree
 # is not considered.
 
 for child in self.getAllChildren():
 if child.getName() == name:
 return child

 def findChildren(self, name):
 """ Return a list of children with the given name from the tree """

 # Note: this returns a list of all the children of a given
 # name, irrespective of the depth of look-up.
 
 children = []
 
 for child in self.getAllChildren():
 if child.getName() == name:
 children.append(child)

 return children
 
 def getPropertyDict(self):
 """ Return the property dictionary """
 
 d = self.getChild('__properties')
 if d:
 return d.getDict()
 else:
 return {}
 
 def getParent(self):
 """ Return the person who created me """

 return self._father
 
 def __setChildDict(self, child):
 """ Private method to set the dictionary of the child
 object 'child' in the internal dictionary """
 
 d = self[self._name]
 d[child.getName()] = child.getDict()

 def setParent(self, father):
 """ Set the parent object of myself """

 # This should be ideally called only once
 # by the father when creating the child :-)
 # though it is possible to change parenthood
 # when a new child is adopted in the place
 # of an existing one - in that case the existing
 # child is orphaned - see addChild and addChild2
 # methods !
 self._father = father
 
 def setName(self, name):
 """ Set the name of this ConfigInfo object to 'name' """ 

 self._name = name

 def setDict(self, d):
 """ Set the contained dictionary """
 
 self[self._name] = d.copy()
 
 def setAttribute(self, name, value):
 """ Set a name value pair in the contained dictionary """
 
 self[self._name][name] = value

 def getAttribute(self, name):
 """ Return value of an attribute from the contained dictionary """
 
 return self[self._name][name]

 def addChild(self, name, force=False):
 """ Add a new child 'child' with the name 'name'.
 If the optional flag 'force' is set to True, the
 child object is overwritten if it is already there.

 This function returns the child object, whether
 new or existing """
 
 if type(name) != str:
 raise ValueError('Argument should be a string!')
 
 child = self.getChild(name)
 if child:
 # print 'Child %s present!' % name
 # Replace it if force==True
 if force:
 index = self.getIndex(child)
 if index != -1:
 child = self.__class__(name)
 self._children[index] = child
 child.setParent(self)
 
 self.__setChildDict(child)
 return child
 else:
 child = self.__class__(name)
 child.setParent(self)
 
 self._children.append(child)
 self.__setChildDict(child)

 return child
 
 def addChild2(self, child):
 """ Add the child object 'child'. If it is already present,
 it is overwritten by default """
 
 currChild = self.getChild(child.getName())
 if currChild:
 index = self.getIndex(currChild)
 if index != -1:
 self._children[index] = child
 child.setParent(self)
 # Unset the existing child's parent
 currChild.setParent(None)
 del currChild
 
 self.__setChildDict(child)
 else:
 child.setParent(self) 
 self._children.append(child)
 self.__setChildDict(child)

if __name__=="__main__":
 window = CompositeDict('Window')
 frame = window.addChild('Frame')
 tfield = frame.addChild('Text Field')
 tfield.setAttribute('size','20')
 
 btn = frame.addChild('Button1')
 btn.setAttribute('label','Submit')

 btn = frame.addChild('Button2')
 btn.setAttribute('label','Browse')

 # print(window)
 # print(window.Frame)
 # print(window.Frame.Button1)
 # print(window.Frame.Button2)
 print(window.Frame.Button1.label)
 print(window.Frame.Button2.label)