Composite Design Pattern in Python
Write a Python program to implement Composite Design Pattern.
# We are attempting to make a Menu with sub-items, which may have subsequent sub-items, such as:
# TopLevelMenu [Composite]
# SubMenuItem1 [Composite]
# SubMenuItem11 [Child]
# SubMenuItem12 [Child]
# SubMenuItem2 [Composite]
class ChildElement:
'''Class representing objects at the bottom of the hierarchy tree.'''
def __init__(self, *args):
''''Takes the first positional argument and assigns to member variable "name".'''
self.name = args[0]
def printDetails(self):
'''Prints the name of the child element.'''
print("\t", end = "")
print(self.name)
class CompositeElement:
'''Class representing objects at any level of the hierarchy tree except for the bottom level.
Maintains the child objects by adding and removing them from the tree structure.'''
def __init__(self, *args):
'''Takes the first positional argument and assigns to member variable "name". Initializes a list of children elements.'''
self.name = args[0]
self.children = []
def appendChild(self, child):
'''Adds the supplied child element to the list of children elements "children".'''
self.children.append(child)
def removeChild(self, child):
'''Removes the supplied child element from the list of children elements "children".'''
self.children.remove(child)
def printDetails(self):
'''Prints the details of the component element first. Then, iterates over each of its children, prints their details by calling their printDetails() method.'''
print(self.name)
for child in self.children:
print("\t", end = "")
child.printDetails()
### CREATING THE MENU i.e. TREE DATA STRUCTURE ###
topLevelMenu = CompositeElement("TopLevelMenu")
subMenuItem1 = CompositeElement("SubMenuItem1")
subMenuItem2 = CompositeElement("SubMenuItem2")
subMenuItem11 = ChildElement("SubMenuItem11")
subMenuItem12 = ChildElement("SubMenuItem12")
subMenuItem1.appendChild(subMenuItem11)
subMenuItem1.appendChild(subMenuItem12)
topLevelMenu.appendChild(subMenuItem1)
topLevelMenu.appendChild(subMenuItem2)
topLevelMenu.printDetails()
##OUTPUT:
##TopLevelMenu
## SubMenuItem1
## SubMenuItem11
## SubMenuItem12
## SubMenuItem2
See also:
- Python 101
- Object Oriented Python
- Design Patterns in Python
- 50+ Handy Standard Library Modules
- 60+ Handy Third Library Modules
- 50+ Tips & Tricks for Python Developers
- 50+ Know-How(s) Every Pythonista Must Know