PrettyPrintTree

This package allows you to print trees (the datastructure) and linked-lists in a readable fashion.
It supports trees with any kind of data, as long it can be turned into a string.
And even supports multi-lined nodes (strings with \n).

Table Of Contents

• Requirements
• Install
• Import
• Documentation
• Example
  • Tree
  • Linked List
• Other Settings
  • Horizontal
  • Trim
  • Return Instead of Print
  • Color
  • Border
  • Escape NewLines
  • Max Depth
  • Start Message
  • Dictionaries \ JSON
  • Labels
• Advanced Examples
  • Binary Tree
  • Filtering
• C#
• Java

Requirements

Python 3.7 and up

Install

You can easily install PrettyPrintTree via pip:

pip install PrettyPrintTree

Import

Once installed, you can import it in your Python script:

from PrettyPrint import PrettyPrintTree

Documentation

To ensure flexibility, PrettyPrintTree requires you to define how to print your specific tree structure. This is achieved by providing two callable functions (lambdas):

1. get_children: This function, given a node of your tree type, returns an iterable of all its children, from left to right. For instance, if your tree implementation looks like this:

   class Tree:
       def __init__(self, val):
           self.val = val
           self.children = []
   

   Your get_children function would be as simple as:

   lambda node: node.children
   

2. get_value: Given a node of your tree type, this function should return that node's value.
   For a tree implementation like this:

   class Tree:
       def __init__(self, val):
           self.val = val
   

   The get_value function would be:

   lambda node: node.val
   

   Note: if the value of the tree doesn't implement __str__, the get_value function should convert it into a string.

To print the tree, you first need to create a PrettyPrintTree object by providing your lambdas and any additional settings. You can then call this object whenever needed without repeatedly specifying the lambdas.

Linked Lists

Printing a linked-list is similar, instead of get_children you will need:
get_next: This function, given a node of your linked-list type, returns the next node.

And optionally:
get_prev: Given a node of your linked-list type, this function should return the previous node.

Example

Tree

from PrettyPrint import PrettyPrintTree


class Tree:
    def __init__(self, value):
        self.val = value
        self.children = []

    def add_child(self, child):
        self.children.append(child)
        return child


pt = PrettyPrintTree(lambda x: x.children, lambda x: x.val)
tree = Tree(1)
child1 = tree.add_child(Tree(2))
child2 = tree.add_child(Tree(3))
child1.add_child(Tree(4))
child1.add_child(Tree(5))
child1.add_child(Tree(6))
child2.add_child(Tree(7))
pt(tree)

Linked List

from PrettyPrint import PrettyPrintLinkedList

class Node:
    def __init__(self, val):
        self.val = val
        self.next_node = None
        self.prev_node = None


n1, n2, n3, n4 = Node("Node1"), Node("Node2"), Node("Node\nJs"), Node("Node4")
n1.next_node = n2
n2.next_node = n3
n3.next_node = n4
n3.prev_node = n2
pt = PrettyPrintLinkedList(
    lambda x: x.val,
    lambda x: x.next_node,
    lambda x: x.prev_node,
    orientation=PrettyPrintLinkedList.Horizontal,
)
pt(n1)

Other Settings

These settings can either be set when initializing the PrettyPrintTree object or when calling the function (which will override the initial setting)

Horizontal

You can print trees from left to right instead of the default top-to-bottom layout:

pt = PrettyPrintTree(
    lambda x: x.children, 
    lambda x: x.val, 
    orientation=PrettyPrintTree.Horizontal
)

Trim

If you want to print only a limited number of characters from each node to keep the tree concise and readable, you can use the trim setting:

pt = PrettyPrintTree(lambda x: x.children, lambda x: x.val, trim=5)

To use a different trim symbol instead of ..., you can do this:

pt = PrettyPrintTree(
    lambda x: x.children, lambda x: x.val, trim=5,
    trim_symbol=' ' + colorama.Back.GREEN
)

Return Instead of Print

If you prefer to get the tree as a string instead of printing it directly, you can enable the return_instead_of_print setting:

to_str = PrettyPrintTree(lambda x: x.children, lambda x: x.val, return_instead_of_print=True)
tree_as_str = to_str(tree)

Color

You can change the background color of each node or opt for no color at all:

from colorama import Back

pt = PrettyPrintTree(lambda x: x.children, lambda x: x.val, color=Back.BLACK)

For no color:

pt = PrettyPrintTree(lambda x: x.children, lambda x: x.val, color='')

Border

You can surround each node with a border:

pt = PrettyPrintTree(lambda x: x.children, lambda x: x.val, border=True)

Escape NewLines

To print each node on one line, you can escape the newline characters:

pt = PrettyPrintTree(lambda x: x.children, lambda x: x.val, show_newline_literal=True)

In order to distinguish between \n and \n you can highlight the \n's:

PrettyPrintTree(
    lambda x: x.children, lambda x: x.val,
    show_newline_literal=True,
    newline_literal=colorama.Fore.LIGHTGREEN_EX + '\\n' + colorama.Fore.RESET
)

Max Depth

Limit the depth to control how many levels of nodes are printed:

pt = PrettyPrintTree(lambda x: x.children, lambda x: x.val, max_depth=10)

Note: the head node has a depth of 0

Start Message

You can add a message to be printed before the tree. Use a lambda that receives the tree and returns a message:

pt = PrettyPrintTree(
    lambda x: x.children, 
    lambda x: x.val, 
    start_message=lambda node: f'printing tree of type {node.typ}:'
)

Dictionaries \ JSON

PrettyPrintTree can also print JSON structures, although they need to be converted into a dictionary, list, or tuple first:

some_json = {'foo': 1, 'bar': ('a', 'b'), 'qux': {'foo': 1, 'bar': ['a', 'b']}}
pt = PrettyPrintTree()
pt.print_json(some_json, name="DICT")

Labels

You can label the branches in your tree by providing a lambda that returns a label between the node and its parent. Use None or False if no label is needed:

pt = PrettyPrintTree(
    lambda x: x.children, 
    lambda x: x.val, 
    lambda x: x.label
)

You can even apply color to the labels using label_color:

from colorama import Back

pt = PrettyPrintTree(
    lambda x: x.children, 
    lambda x: x.val, 
    lambda x: x.label,
    label_color=Back.BLACK
)

Advanced Examples

Binary Tree

Here's how to print a binary tree:

class Tree:
    def __init__(self, val):
        self.val = val
        self.right = None
        self.left = None

One approach is to define get_children as follows:

PrettyPrintTree(
    lambda x: [x for x in [x.prev_node, x.next_node] if x is not None],
    lambda x: x.val
)

However, this approach does not preserve the direction of the children when only one child is present. For better results, use this approach:

PrettyPrintTree(
    lambda x: [] if x is None or x.prev_node is x.next_node is None else [x.prev_node, x.next_node],
    lambda x: x.val if x else (colorama.Back.BLACK + '   ' + colorama.Back.LIGHTBLACK_EX)
)

Filtering

You can easily filter specific nodes by adding a filter in the get_children lambda:

PrettyPrintTree(lambda node: filter(lambda n: "to print" in str(n.val), node.children), ...

PrettyPrintTree(lambda node: [n for n in node.children if n.val > 3.141], ...

C#

A C# version of PrettyPrintTree is also available: https://github.com/AharonSambol/PrettyPrintTreeCSharp

Java

A Java version of PrettyPrintTree is also available: https://github.com/AharonSambol/PrettyPrintTreeJava