How do I change the "position" of an edge in networkx?

Question

(Label the nodes as 1 to 4 clockwise starting on the top left)

How do I change the edge 13 to make it go "outside" the square, like the graph on the right, in networkx?

(Note: I am not asking for the function "draw_planar")

Thanks

Answer 1

A possible option would be to use Connection styles for annotations.

You can start by drawing the nodes in a classic way :

fig, ax = plt.subplots(figsize=(4, 4))

nx.draw_networkx_nodes(
    G, pos, ax=ax,
    node_color="lime", alpha=0.4, edgecolors="black",
)

nx.draw_networkx_labels(G, pos, ax=ax)

Then proceed with the edges in two steps, to implement the connectionstyle:

RADIUS = 1.2
EDGE_TO_BEND = (1, 3)

nx.draw_networkx_edges(
    G, pos, ax=ax, edgelist=[e for e in G.edges() if e != EDGE_TO_BEND]
)

nx.draw_networkx_edges(
    G, pos, ax=ax, edgelist=[EDGE_TO_BEND],
    edge_color="tab:red", width=4, alpha=0.5,
    arrows=True, connectionstyle=f"arc3,rad={RADIUS}",
)

ax.axis("off")

plt.show()

Graph used (G):

import networkx as nx

G = nx.Graph([(1, 2), (2, 3), (3, 4), (4, 1), (1, 3), (2, 4)])

pos = {1: (0, 1), 2: (1, 1), 3: (1, 0), 4: (0, 0)} # square-shape