em#

Functions

from_condensed_em_notation(data[, ...])

Parse condensed EM notation into a planar diagram.

from_em_notation(data[, oriented])

Create a planar diagram from EM dict (or stringified dict) notation.

to_condensed_em_notation(g[, separator])

Return condensed EM notation for diagrams with single-letter node labels.

to_em_notation(g)

Return EM dict notation of a planar diagram.
to_em_notation(g)#

Return EM dict notation of a planar diagram.

For each node, returns a CCW-ordered list of (neighbor, neighbor_pos) tuples. This uses the diagram’s endpoint “twin” relation to find the adjacent endpoint.

Parameters:

g (PlanarDiagram) – Planar diagram.

Returns:

dict – Mapping node -> [(neighbor, neighbor_pos), ...].

Return type:

Dict[Any, list[tuple[Any, int]]]

Examples

>>> from knotpy.classes.planardiagram import PlanarDiagram
>>> d = PlanarDiagram()
>>> d.add_vertices_from(["a", "b"])
>>> d.set_arc((("a", 0), ("b", 0)))
>>> em = to_em_notation(d)
>>> em["a"] == [("b", 0)]
True
from_em_notation(data, oriented=False)#

Create a planar diagram from EM dict (or stringified dict) notation.

The input should map each node to a CCW-ordered list of (neighbor, neighbor_position) pairs.

Parameters:

  • data (Mapping[Any, Iterable[tuple[Any, int]]] | str) – EM dict, or a string that safely evaluates to such a dict.

  • oriented (bool) – Whether to construct an oriented diagram (not implemented).

Returns:

PlanarDiagram – Parsed diagram.

Raises:

  • NotImplementedError – If oriented=True.

  • ValueError – On malformed inputs.

Return type:

PlanarDiagram

to_condensed_em_notation(g, separator=',')#

Return condensed EM notation for diagrams with single-letter node labels.

Constraints:

  • Nodes must be sortable and of the same type (e.g., all strings or all ints).

  • At most 52 nodes (a–zA–Z).

Parameters:

  • g (PlanarDiagram) – Diagram to serialize.

  • separator (str) – Token separator (default: comma).

Returns:

str – Condensed EM string (alphabetical node order).

Raises:

  • ValueError – If node count exceeds 52.

  • TypeError – If nodes are not mutually comparable for sorting.

Return type:

str

from_condensed_em_notation(data, separator=',', oriented=False)#

Parse condensed EM notation into a planar diagram.

Token format per node (CCW): <neighbor-letter><neighbor-position>.... Nodes are assigned in alphabetical order: a, b, c, …

Parameters:

  • data (str) – Condensed EM string.

  • separator (str) – Token separator used in the string (default: comma).

  • oriented (bool) – Whether to construct an oriented diagram (not implemented).

Returns:

PlanarDiagram – Parsed diagram.

Raises:

  • NotImplementedError – If oriented=True.

  • ValueError – For malformed tokens.

Return type:

PlanarDiagram