# python-igraph Manual

For using igraph from Python

# Spanning Trees¶

This example shows how to generate a spanning tree from an input graph using `spanning_tree()`. For the related idea of finding a minimum spanning tree, see Minimum Spanning Trees.

First we create a 6 by 6 lattice graph.

```import igraph as ig
import matplotlib.pyplot as plt
import random

g = ig.Graph.Lattice([6, 6], circular=False)
```

As an optional step, we randomly rearrange some of the vertex IDs with `permute_vertices()` in order to generate a more interesting spanning tree.

```# Optional: Rearrange the vertex ids to get a more interesting spanning tree
layout = g.layout("grid")

random.seed(0)
permutation = list(range(g.vcount()))
random.shuffle(permutation)
g = g.permute_vertices(permutation)

# Calculate the new layout coordinates based on the permutation
new_layout = g.layout("grid")
for i in range(36):
new_layout[permutation[i]] = layout[i]
layout = new_layout
```

Finally, we generate the spanning tree and display it. Note that we use `None` as our weights value, to indicate that we any spanning tree in the graph will do.

```# Generate spanning tree
spanning_tree = g.spanning_tree(weights=None, return_tree=False)

# Plot graph
g.es["color"] = "lightgray"
g.es[spanning_tree]["color"] = "midnightblue"
g.es["width"] = 0.5
g.es[spanning_tree]["width"] = 3.0

fig, ax = plt.subplots()
ig.plot(
g,
target=ax,
layout=layout,
vertex_color="lightblue",
edge_width=g.es["width"]
)
plt.show()
```

The final plot looks like this: