pd#

Functions

`from_condensed_pd_notation`(text[, ...])	Create a planar diagram from condensed PD code (e.g., `"abc bcde ..."`).
`from_pd_notation`(text[, node_type, oriented])	Create a planar diagram from PD notation.
`to_condensed_pd_notation`(k)	Serialize a planar diagram to condensed PD notation.
`to_pd_notation`(k)	Serialize a planar diagram to PD notation.

from_pd_notation(text, node_type=<class 'str'>, oriented=False, **attr)#

Create a planar diagram from PD notation.

Supports Mathematica, KnotInfo, and Topoly variants. Nodes default to 'a','b','c',... if node_type is str; otherwise integers are used in order of appearance.

Parameters:

text (str) – PD notation string (mixed styles allowed; auto-detected).
node_type (type | Any) – Use str for a,b,c,... labels (default), or a different marker to keep integers.
oriented (bool) – Whether to create an oriented diagram (not implemented yet).
**attr (Any) – Diagram attributes to set (e.g., name, framing).

Returns:

PlanarDiagram – Parsed diagram.

Raises:

NotImplementedError – If oriented=True (placeholder).
ValueError – If the PD string is malformed or arcs are not paired.

Return type:

PlanarDiagram

Examples

>>> s = "V[1,2,3], X[2,3,4,5]"
>>> d = from_pd_notation(s)
>>> isinstance(d, PlanarDiagram)
True

to_pd_notation(k)#

Serialize a planar diagram to PD notation.

Output uses abbreviations inferred by node type: X[...,...,...,...] for crossings and V[...] for vertices. Arc ids are assigned by enumerating unique arcs as they appear.

Parameters:: k (PlanarDiagram) – Diagram to serialize.
Returns:: str – PD notation string.
Return type:: str

Examples

>>> from knotpy.classes.planardiagram import PlanarDiagram
>>> d = PlanarDiagram()
>>> d.add_vertices_from(["a","b"])
>>> d.set_arc((("a",0),("b",0)))
>>> out = to_pd_notation(d)
>>> out.startswith("V[") or out.startswith("X[")
True

to_condensed_pd_notation(k)#

Serialize a planar diagram to condensed PD notation.

Constraints:

At most 50 arcs (since we label arcs with single letters).
Diagram must contain only vertices and crossings.
No vertex may have degree 4 (ambiguity with crossings).

Parameters:: k (PlanarDiagram) – Diagram to serialize.
Returns:: str – Space-separated tokens of arc letters per node (CCW).
Raises:: ValueError – If constraints are violated.
Return type:: str

from_condensed_pd_notation(text, node_type=<class 'str'>, oriented=False, **attr)#

Create a planar diagram from condensed PD code (e.g., "abc bcde ...").

Each token is a node’s incident arcs in CCW order; 4 letters → X (crossing), otherwise V (vertex). Arc labels must be single characters and paired globally.