pd-code-components

Find the components represented by a planar-diagram code.

Installation

pip install pd-code-components

Usage example

from pd_code_components import get_components_from_pd_code

hopf = [[2, 3, 1, 4], [4, 1, 3, 2]]
print(get_components_from_pd_code(hopf))
# [[1, 2], [3, 4]]

Algorithm

At each crossing, slots 0 and 2 belong to one strand and slots 1 and 3 to the other. These opposite-slot pairs form an undirected graph on arc labels. Iterative depth-first traversal finds connected components in O(V + E) time. Sets are used for adjacency and visitation, avoiding the quadratic membership checks in the original list-based implementation.

Input conventions

A PD code is represented as a list of four-entry crossings. Arc labels normally occur exactly twice. Public functions validate inputs and return new values rather than mutating caller-owned data unless their API explicitly says otherwise.

External software

No external software is required.

Development

Run examples and package checks before release. Python packages require Python 3.10 or newer. Build PyPI artifacts with:

poetry check
poetry build

License

MIT. See LICENSE.