I’ve made a simple python package called recursion-visualiser which you can install via pip that helps you to easily trace function calls for any arbitary recursive function and save tree as gif and png image by simply adding a decorator to your function.

Let's draw the tree for recursive Fibonacci function. Here is the recursive code:

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))

if __name__ == "__main__":
    main()

Now let's modify the code to draw recursion tree. First let's draw a very minimalist example

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

# Add decorator
@vs()
def fib(n):
    if n <= 1:
        return n
    return fib(n=n - 1) + fib(n=n-2)

def main():
    print(fib(n=6))
    vs.make_animation("fibonacci.gif", delay=2)

if __name__ == "__main__":
    main()

The output file is saved as fibonacci.gif and fibonacci.png. Here is how output animation looks: Also the final image of recursion tree:

We can also make it better using node color and other properties:

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

# Add decorator
@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():
    print(fib(n=6))
    vs.make_animation("fibonacci.gif", delay=2)

if __name__ == "__main__":
    main()

Here is the output which looks much better:

Here is the final image of the recursion tree:

Check out more examples at here