# Python Program to Construct a Tree & Perform Insertion, Deletion, Display

PythonServer Side ProgrammingProgramming

When it is required to construct a binary tree, and perform operations such as inserting an element, deleting an element and displaying elements of the tree, a class is defined with methods in it. An instance of the class is defined and this is used to access the elements and perform operations.

Below is a demonstration of the same −

## Example

Live Demo

class Tree_struct:
def __init__(self, data=None, parent=None):
self.key = data
self.children = []
self.parent = parent

def set_root(self, data):
self.key = data

self.children.append(node)

def search_node(self, key):
if self.key == key:
return self
for child in self.children:
temp = child.search_node(key)
if temp is not None:
return temp
return None

def remove_node(self):
parent = self.parent
index = parent.children.index(self)
parent.children.remove(self)
for child in reversed(self.children):
parent.children.insert(index, child)
child.parent = parent

def bfs(self):
queue = [self]
while queue != []:
popped = queue.pop(0)
for child in popped.children:
queue.append(child)
print(popped.key, end=' ')

my_instance = None

print('Menu (this assumes no duplicate keys)')
print('remove <data>')
print('display')
print('quit')

while True:
do = input('What would you like to do? ').split()

operation = do[0].strip().lower()
data = int(do[1])
new_node = Tree_struct(data)
suboperation = do[2].strip().lower()
if suboperation == 'at':
my_instance = new_node
elif suboperation == 'below':
position = do[3].strip().lower()
key = int(position)
ref_node = None
if my_instance is not None:
ref_node = my_instance.search_node(key)
if ref_node is None:
print('No such key.')
continue
new_node.parent = ref_node

elif operation == 'remove':
data = int(do[1])
to_remove = my_instance.search_node(data)
if my_instance == to_remove:
if my_instance.children == []:
my_instance = None
else:
leaf = my_instance.children[0]
while leaf.children != []:
leaf = leaf.children[0]
leaf.parent.children.remove_node(leaf)
leaf.parent = None
leaf.children = my_instance.children
my_instance = leaf
else:
to_remove.remove_node()

elif operation == 'display':
if my_instance is not None:
print('Breadth First Search traversal is : ', end='')
my_instance.bfs()
print()
else:
print('The tree is empty')

elif operation == 'quit':
break

## Output

Menu (this assumes no duplicate keys)
remove <data>
display
quit
What would you like to do? add 5 at root
What would you like to do? add 6 below 5
What would you like to do? add 8 below 6
What would you like to do? remove 8
What would you like to do? display
Breadth First Search traversal is : 5 6
What would you like to do? quit

## Explanation

• The ‘Tree_struct’ class with required attributes is created.

• It has an ‘init’ function that is used to create an empty list.

• Another method named ‘set_root’ is defined to specify the root of the tree.

• Another method named ‘add_node’ is defined that helps add nodes to the tree.

• Another method named ‘search_node’ is defined that helps search for a specific element.

• A method named ‘remove_node’ is defined, that deletes elements from the tree.

• Another method named ‘bfs’ is defined, that helps perform breadth first search on the tree.

• An instance is created and assigned to ‘None’.

• The user input is taken for the operation that needs to be performed.

• Depending on the user’ choice, the operation is performed.

• Relevant output is displayed on the console.

Published on 15-Apr-2021 13:47:30