Recursion visualiser is a python tool that visualizes recursion tree with animation and draws recursion tree for recursive function. It works with almost any type of recursive function. Just add the recursion-visualiser decorator to your function and let it do the rest of the work.

The only dependency for recursion visualiser is Graphviz

• Download graphviz binary
• Add graphviz bin to path manually or by adding the following line on your script. Change the installation directory according to your installation path

# Set it to bin folder of graphviz  
os.environ["PATH"] += os.pathsep +  'C:/Program Files (x86)/Graphviz2.38/bin/'  

• Install graphviz

 sudo apt install graphviz

The instructions to install graphviz for other operating system is available here

The easiest way to install recursion-visualiser package is from pypi

pip install recursion-visualiser

An alternative way is to clone the repository and install all the requirements.

pip install -r requirements.txt

If you have docker and docker-compose installed then you can install recursion-tree-visualiser using Docker and docker-compose.yml file

1. Download Docker file from repo

curl https://raw.githubusercontent.com/Bishalsarang/Recursion-Tree-Visualizer/master/Dockerfile --output Dockerfile

1. Download docker-compose.yml

curl https://raw.githubusercontent.com/Bishalsarang/Recursion-Tree-Visualizer/master/docker-compose.yml --output docker-compose.yml

1. Start docker container

CURRENT_UID=$(id -u):$(id -g) docker-compose up

1. Run any python scripts and run using

docker-compose exec vs python fibonacci.py

The preferred way to import the decorator class from the package is as:

from visualiser.visualiser import Visualiser as vs

Let's draw the recursion tree for fibonacci number.
Here is how the simple code looks like

def fib(n):  
    if n <= 1: 
        return n 
    return fib(n - 1) + fib(n - 2)  

print(fib(6))  

Now we want to draw the recursion tree for this function. It is as simple as adding a decorator

# Author: Bishal Sarang

# Import Visualiser class from module visualiser
from visualiser.visualiser import Visualiser as vs

# Add decorator
# Decorator accepts optional arguments: ignore_args , show_argument_name, show_return_value and node_properties_kwargs
@vs(node_properties_kwargs={"shape":"record", "color":"#f57542", "style":"filled", "fillcolor":"grey"})
def fib(n):
    if n <= 1:
        return n
    return fib(n=n - 1) + fib(n=n - 2)


def main():
    # Call function
    print(fib(n=6))
    # Save recursion tree to a file
    vs.make_animation("fibonacci.gif", delay=2)


if __name__ == "__main__":
    main()

Here are the changes required:

• Add decorator Visualiser which accepts optional arguments ignore_args, show_argument_name and 'show_return_value'
• Change every function calls to pass as keyword arguments.
• Make_animation

The output image are saved as "fibonacci.gif" and "fibonacci.png"

Here is how the recursion tree looks like:
Animation:

Find other examples here and read more about recursion-visualiser here

• Minimal working version
• Upload package to pypi
• Support animation
• Add node styles
• Support aliasing for function name
• Show repeated states
• Support node_color, backgroundcolor etc
• Refactor
• Handle base cases
• Make more beautiful trees