graphlib2

This is a Rust port of Python's stdlib graphlib. It passes all of the standard libraries tests and is a drop in replacement. This also happens to be Python 3.7 compatible, so it can be used as a backport. Since usage is exactly the same as the standard libraries, please refer to their documentation for usage details.

See this project on GitHub.

Example

from graphlib2 import TopologicalSorter

graph = {0: [1], 1: [2]}  # 0 depends on 1, 1 depends on 2
ts = TopologicalSorter(graph)
ts.prepare()
while ts.is_active():
    ready_nodes = ts.get_ready()
    ts.done(*ready_nodes)  # all at a time or one by one

Motivation

This was primarily written for di and for me to learn Rust. In other words: please vet the code yourself before using this.

Differences with the stdlib implementation

Added TopologicalSorter.copy() which copies a prepared or unprepared graph so that it can be executed multiple times.
Pretty solid performance improvements (see benchmarks).
Misc improvements, like working generics without postponed evaluation (ToplologicalSorter[int] works at runtime).

Performance

The implementation was designed for the specific use case of adding all nodes, calling prepare() then copying and executing in a loop:

from graphlib2 import TopologicalSorter

graph = {0: [1], 1: [2]}
ts = TopologicalSorter(graph)
ts.prepare()
while True:  # hot loop
    t = ts.copy()
    while t.is_active():
        ready_nodes = t.get_ready()
        t.done(*ready_nodes)

This means that the focus is on the performance of TopologicalSorter.get_ready() and TopologicalSorter.done(), and only minimal effort was put into other methods (prepare(), add() and get_static_order()), although these are still quite performant.

Contributing

Clone the repo.
Run make init
Run make test
Make your changes
Push and open a pull request
Wait for CI to run.