PrettyPrintTree 1.36.4

A tool to print trees to the console

PrettyPrintTree

This package allows you to print the tree datastructure in a readable fashion (in Python).

It supports trees with any kind of data (as long it can be turned into a string).

And even supports multi lined nodes (as in strings with \n).

Supported Python Version

Python 3.7 and up

Install

pip install PrettyPrintTree

Import

from PrettyPrint import PrettyPrintTree

Documentation

I tried to make this as flexible as possible, so in order to support multiple types of trees you need to explain to the program how to print your tree. The way to accomplish this is by passing 2 lambdas (or any other Callable):

1. get_children: Given a node of your tree type returns an iterable of all its children (from left to right).

   For example if this is your tree implementation:

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

   Then get_children would be as simple as:

   lambda node: node.children
   

2. get_value: Given a node of your tree type returns that node's value.

   For this tree implementation:

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

   The get_value would be:

   lambda node: node.val
   

   (if the value of the tree doesn't implement __str__ get_value should turn it into a string)

In order to print the tree you first need to make a PrettyPrintTree object which you pass your lambdas (and any other settings) to, then you can call it whenever you want without needing to pass the lambdas each time.

Examples

Simple Ttree

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)

Binary Tree

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

One approach would be:

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

Although this won't preserve the direction of the children in the event that only one child is present.
A different approach would be:

PrettyPrintTree(
    lambda x: [] if x is None or x.left is x.right is None else [x.left, x.right],
    lambda x: x.val if x else None
)

Other Settings

Horizontal

You can print trees from left to right (instead of up to down)

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

or

pt(node, orientation=PrettyPrintTree.HORIZONTAL)

Trim

Say you only want to print the first few characters of each node (in order to keep the tree small for readability), then you can set trim to a specific amount of characters.

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

Return Instead of Print

Instead of printing the tree it can return the string instead if you prefer.

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 bg color of each node, or even just not use color.

from colorama import Back

# change color to black:
pt = PrettyPrintTree(lambda x: x.children, lambda x: x.val, color=Back.BLACK)

# without any color:
pt = PrettyPrintTree(lambda x: x.children, lambda x: x.val, color=None)

Border

You can also surround each node with a little border:

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

Escape NewLines

You can escape \n so that each node will be printed on one line.

Note: \n will be escaped into \\n so that you can tell the difference

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

Max Depth

You can specify a max depth so that it will only print nodes up to that depth. This can be done either at the start:

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

Or when calling the function:

pt(tree, max_depth=5)

This will override the max depth set at the start (if any) for this time only. To have no max depth, you can set it to -1.

Start Message

You can give a lambda that will be given the tree and will return a string which will be printed before the tree.

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

Dictionaries \ JSON

Printing JSON is also an option. Although it needs to be turned into dict \ list \ tuple first

some_json = {'foo': 1, 'bar': ('a', 'b'), 'qux': {'foo': 1, 'bar': ['a', 'b']}}
pt = PrettyPrintTree()
# either:
pt(some_json)
# or:
pt.print_json(some_json, name="DICT", max_depth=10)

Labels

You can also label the branches in your tree.

The label lambda should return a string indicating the label between the node and its parent, if there should be no label then None or False.

NOTE: Currently this only works on vertical trees

NOTE: Each label must be on a single line (no \n)

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

You can even color 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

Filtering

To filter specific nodes all you need to do is add a filter in the get_children lambda, eg:

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#

I made a C# version too: https://github.com/AharonSambol/PrettyPrintTreeCSharp

Java

I made a Java version too: https://github.com/AharonSambol/PrettyPrintTreeJava