Allow creating subgraphs directly from sets of node indices (e.g., those returned by connected components)

[hakkape]

What is the expected enhancement?

Currently, the connected components function returns a list of sets of node indices. If i then try to create a subgraph from each connected component, i get an error because a set is not a sequence. Of course, i can turn the sets into lists or similar first, but this seems unnecessary to me. I find a set a perfectly reasonable container from which to create a subgraph. So the enhancement would be to modify the subgraph function to also accept sets of node indices.

Minimum (currently not working) example:

import rustworkx as rx

# create graph with two connected components
g = rx.PyGraph()
a = g.add_node("A")
b = g.add_node("B")
c = g.add_node("C")
d = g.add_node("D")
g.add_edge(a, b, None)
g.add_edge(c, d, None)
components = rx.connected_components(g)

# create subgraphs 
subgraphs = [g.subgraph(component) for component in components]

(Technically, i would like this modification for directed graph, but it seems sensible for all types)

[IvanIsCoding]

Of course, i can turn the sets into lists or similar first, but this seems unnecessary to me.

This could be fixable with something along the lines of #1292.

With that being said:

rustworkx/src/digraph.rs

Line 3115 in 7385756

pub fn subgraph(&self, py: Python, nodes: Vec<usize>, preserve_attrs: bool) -> PyDiGraph {

is the line

We use the built-in conversion from PyO3. I assume they exploit __len__ and __getitem__ being implemented for Sequence to handle the arbitrary conversions to a Rust Vec<T>. set does not implement __geitem__ (it has no order, after all).

So I am not surprised the conversion fails. If you want things to work, do pass Sequence where we annotate arguments with Sequence. Doing list(component) is a simple fix. I will mark this as a feature request and not a bug, the code is working as intended.