"""
==============
Directed Graph
==============

Basic visualization of a directed graph with manual layout.
"""

import networkx as nx
import matplotlib.pyplot as plt

G = nx.DiGraph([(0, 3), (1, 3), (2, 4), (3, 5), (3, 6), (4, 6), (5, 6)])

options = {
    "font_size": 36,
    "node_size": 3000,
    "node_color": "white",
    "edgecolors": "black",
    "linewidths": 5,
    "width": 5,
}

# group nodes by column
left_nodes = [0, 1, 2]
middle_nodes = [3, 4]
right_nodes = [5, 6]

# set the position according to column (x-coord)
pos = {n: (0, i) for i, n in enumerate(left_nodes)}
pos.update({n: (1, i + 0.5) for i, n in enumerate(middle_nodes)})
pos.update({n: (2, i + 0.5) for i, n in enumerate(right_nodes)})

nx.draw(G, pos, with_labels=True, **options)
plt.show()