https://github.com/aleksandrhovhannisyan/pythongraphcycledetection

Python script for detecting cycles in a directed graph.
https://github.com/aleksandrhovhannisyan/pythongraphcycledetection

algorithm cycle-detection deadlock-detection detecting-cycles graphs python

Last synced: 11 days ago
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Python script for detecting cycles in a directed graph.

• Host: GitHub
• URL: https://github.com/aleksandrhovhannisyan/pythongraphcycledetection
• Owner: AleksandrHovhannisyan
• Created: 2018-11-30T12:47:44.000Z (about 6 years ago)
• Default Branch: master
• Last Pushed: 2019-05-31T18:57:11.000Z (over 5 years ago)
• Last Synced: 2024-11-06T07:27:05.959Z (about 2 months ago)
• Topics: algorithm, cycle-detection, deadlock-detection, detecting-cycles, graphs, python
• Language: Python
• Homepage:
• Size: 26.4 KB
• Stars: 0
• Watchers: 2
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# Python Graph Cycle Detection

A simple Python program to detect cycles in a directed graph. Below is a sample image of the graph used for testing [source: Modern Operating Systems, 4th ed]. The left image shows the original nodes in the graph. The right image shows the reduced graph with all identified cycles.

![Image of a graph from Modern Operating Systems, Chapter 6](graph.PNG)

### Using the Class

The `CycleFinder` class expects to be fed an instance of `DirectedGraph` (see `graph.py`).

This class accepts a dictionary that maps a node to its neighbors. Optionally, you can avoid initializing it with any dictionary and manually `insert` your nodes into the graph.

You'll need the following imports:

`from cycle_finder import CycleFinder`

`from graph import DirectedGraph`

### Testing

See the bottom of `cycle_finder.py` for an example test to identify the cycle in the image above. Note that CycleFinder *will* modify the underlying dictionary once the `findCycles` method is invoked.

Note: If a node does not have any edges originating from it (such as `S` in the sample image provided above), do one of the following:

- If you're initializing a `DirectedGraph` object with a dictionary, then specify that node's neighbors as the empty list (`[]`)

- If you're instead manually inserting start-end pairs, then specify `end` as `None`