Tree plotting in Python

I want to plot trees using Python. Decision trees, Organizational charts, etc. Any library that helps me with that?

I develop ETE, which is a python package intended, among other stuff, for programmatic tree rendering and visualization. You can create your own layout functions and produce custom tree images:

It has a focus on phylogenetics, but it can actually deal with any type of hierarchical tree (clustering, decision trees, etc.)

There's graphviz - http://www.graphviz.org/. It uses the "DOT" language to plot graphs. You can either generate the DOT code yourself, or use pydot - https://github.com/pydot/pydot. You could also use networkx - http://networkx.lanl.gov/tutorial/tutorial.html#drawing-graphs, which make it easy to draw to either graphviz or matplotlib.

networkx + matplotlib + graphviz gives you the most flexibility and power, but you need to install a lot.

If you want a quick solution, try:

Install Graphviz.

open('hello.dot','w').write("digraph G {Hello->World}")
import subprocess
subprocess.call(["path/to/dot.exe","-Tpng","hello.dot","-o","graph1.png"]) 
# I think this is right - try it form the command line to debug

Then you install pydot, because pydot already does this for you. Then you can use networkx to "drive" pydot.

For basic visualization I would consider using treelib,

It is very straightforward and easy to use:

 from treelib import Node, Tree

 tree = Tree()

 tree.create_node("Harry", "harry")  # No parent means its the root node
 tree.create_node("Jane",  "jane"   , parent="harry")
 tree.create_node("Bill",  "bill"   , parent="harry")
 tree.create_node("Diane", "diane"  , parent="jane")
 tree.create_node("Mary",  "mary"   , parent="diane")
 tree.create_node("Mark",  "mark"   , parent="jane")

 tree.show()

Output:

Harry
├── Bill
└── Jane
    ├── Diane
    │   └── Mary
    └── Mark 

Plotly can plot tree diagrams using igraph. You can use it offline these days too. The example below is intended to be run in a Jupyter notebook

import plotly.plotly as py
import plotly.graph_objs as go

import igraph
from igraph import *
# I do not endorse importing * like this

#Set Up Tree with igraph

nr_vertices = 25
v_label = map(str, range(nr_vertices))
G = Graph.Tree(nr_vertices, 2) # 2 stands for children number
lay = G.layout('rt')

position = {k: lay[k] for k in range(nr_vertices)}
Y = [lay[k][1] for k in range(nr_vertices)]
M = max(Y)

es = EdgeSeq(G) # sequence of edges
E = [e.tuple for e in G.es] # list of edges

L = len(position)
Xn = [position[k][0] for k in range(L)]
Yn = [2*M-position[k][1] for k in range(L)]
Xe = []
Ye = []
for edge in E:
    Xe+=[position[edge[0]][0],position[edge[1]][0], None]
    Ye+=[2*M-position[edge[0]][1],2*M-position[edge[1]][1], None] 

labels = v_label

#Create Plotly Traces

lines = go.Scatter(x=Xe,
                   y=Ye,
                   mode='lines',
                   line=dict(color='rgb(210,210,210)', width=1),
                   hoverinfo='none'
                   )
dots = go.Scatter(x=Xn,
                  y=Yn,
                  mode='markers',
                  name='',
                  marker=dict(symbol='dot',
                                size=18, 
                                color='#6175c1',    #'#DB4551', 
                                line=dict(color='rgb(50,50,50)', width=1)
                                ),
                  text=labels,
                  hoverinfo='text',
                  opacity=0.8
                  )
                  
# Create Text Inside the Circle via Annotations

def make_annotations(pos, text, font_size=10, 
                     font_color='rgb(250,250,250)'):
    L=len(pos)
    if len(text)!=L:
        raise ValueError('The lists pos and text must have the same len')
    annotations = go.Annotations()
    for k in range(L):
        annotations.append(
            go.Annotation(
                text=labels[k], # or replace labels with a different list 
                                # for the text within the circle  
                x=pos[k][0], y=2*M-position[k][1],
                xref='x1', yref='y1',
                font=dict(color=font_color, size=font_size),
                showarrow=False)
        )
    return annotations  
    
# Add Axis Specifications and Create the Layout

axis = dict(showline=False, # hide axis line, grid, ticklabels and  title
            zeroline=False,
            showgrid=False,
            showticklabels=False,
            )

layout = dict(title= 'Tree with Reingold-Tilford Layout',  
              annotations=make_annotations(position, v_label),
              font=dict(size=12),
              showlegend=False,
              xaxis=go.XAxis(axis),
              yaxis=go.YAxis(axis),          
              margin=dict(l=40, r=40, b=85, t=100),
              hovermode='closest',
              plot_bgcolor='rgb(248,248,248)'          
              )
              
# Plot

data=go.Data([lines, dots])
fig=dict(data=data, layout=layout)
fig['layout'].update(annotations=make_annotations(position, v_label))
py.iplot(fig, filename='Tree-Reingold-Tilf')
# use py.plot instead of py.iplot if you're not using a Jupyter notebook

Output

For a 2021 solution, I wrote a Python wrapper of the TreantJS library. The package creates an HTML file with a tree visualization. The user can optionally invoke R's webshot library to render high-res screenshots of the trees. The package is quite new, so any PRs, bug reports, or feature requests in the issues would be much appreciated! See: https://github.com/Luke-Poeppel/treeplotter.

The package has some annoying installation requirements (see Installation.md), so I wrote a MacOS installation helper (tested on Catalina and Big Sur). Any tips on reducing these constraints would also be welcome.

It's expirmental, but Google has a GraphViz api. It's convenient if you just want to quickly visualize a graph, but don't want to install any software.