4.1.1.3.1.5. pyfem.fem.NodeSet module

Bases: itemList

Container for nodes and node groups.

Inherits from itemList to store nodal coordinates indexed by node ID. Maintains nodal coordinates, spatial dimensionality (rank), and named groupings read from legacy .pro files or Gmsh meshes. Provides convenience methods for retrieving coordinates and iterating group contents.

rank

Spatial dimension of the mesh (2 for 2D, 3 for 3D). Initialized to -1 and set automatically when first node is added.

Type:: int

groups

Dictionary mapping group names to lists of node IDs. Groups are typically used to define boundary conditions (e.g., ‘Left’, ‘Right’, ‘Top’, ‘Bottom’).

Type:: Dict[str, List[int]]

Notes

The NodeSet class extends itemList, inheriting methods like add(), get(), and __len__(). Node coordinates are stored internally and can be retrieved via getNodeCoords().

Examples

>>> nodes = NodeSet()
>>> nodes.add(0, [0.0, 0.0])      # Add node 0 at origin
>>> nodes.add(1, [1.0, 0.0])      # Add node 1 at (1, 0)
>>> nodes.addToGroup('Bottom', 0)
>>> nodes.addToGroup('Bottom', 1)
>>> coords = nodes.getNodeCoords('Bottom')

getNodeCoords(nodeIDs: int | List[int] | str) → array[source]

Return coordinates for one or more nodes as a NumPy array.

Parameters:: nodeIDs (Union[int, List[int], str]) – Single node ID (int), list of node IDs (list), or node group name (str). When a string is provided, it references a node group defined in the model.
Returns:: Array containing nodal coordinates. For a single node, returns a 1D array of shape (rank,). For multiple nodes, returns a 2D array of shape (n, rank) where n is the number of nodes and rank is the spatial dimension.
Return type:: numpy.array

Examples

>>> nodes.getNodeCoords(5)           # Single node
array([1.0, 2.0, 0.0])

>>> nodes.getNodeCoords([1, 2, 3])   # Multiple nodes
array([[0.0, 0.0, 0.0],
       [1.0, 0.0, 0.0],
       [2.0, 0.0, 0.0]])

>>> nodes.getNodeCoords('Left')      # Node group
array([[0.0, 0.0, 0.0],
       [0.0, 1.0, 0.0]])

getNodeIDs(groupName: str) → List[int][source]

Return list of node IDs in the specified group.

Parameters:: groupName (str) – Name of the node group.
Returns:: List of node IDs in the specified group.
Return type:: List[int]

Examples

>>> nodes.getNodeIDs('Left')
[0, 1, 2]

readFromFile(fname: str) → None[source]

Read nodes and groups from legacy .pro file format.

Parses the input file twice: first pass reads nodal coordinates from <Nodes> blocks or references external Gmsh files; second pass reads <NodeGroup> definitions. Duplicate nodes in groups are automatically removed.

Parameters:: fname (str) – Path to input file (.pro format or referencing a Gmsh file).

Notes

Supported file formats: 1. Native .pro format with <Nodes> and <NodeGroup> blocks 2. Gmsh reference: line containing ‘gmsh = “filename.msh”’

The file is parsed line by line. Comments and whitespace are handled. Node groups are deduplicated after reading.

readGmshFile(fname: str) → None[source]

Read nodes and groups from a Gmsh mesh file.

Uses meshio to parse Gmsh format and extract nodes and physical groups. Automatically detects spatial dimension (2D/3D) based on element types. Physical groups from Gmsh become node groups in PyFEM.

Parameters:: fname (str) – Path to the Gmsh file (.msh format, versions 2 or 4).

Notes

3D element detection: - Checks for prisms, pyramids, hexahedra, wedges, and tetrahedra - Sets rank=3 if any 3D elements found, otherwise rank=2

Node groups are populated from Gmsh’s cell_sets_dict, with ‘gmsh:bounding_entities’ excluded. All nodes in elements belonging to a physical group are added to the corresponding PyFEM group.

Requires: - meshio package for reading Gmsh files

addToGroup(modelType: str, ID: int | str) → None[source]

Register a node ID to a named group.

Creates the group if it doesn’t exist, otherwise appends the node to the existing group. String node IDs are automatically converted to integers.

Parameters:

modelType (str) – Name of the node group (e.g., ‘Left’, ‘Right’, ‘Bottom’, ‘Top’).
ID (Union[int, str]) – Node identifier. String values are converted to int.

Examples

>>> nodes.addToGroup('Boundary', 5)
>>> nodes.addToGroup('Boundary', '10')  # String converted to int

logInfo() → None[source]

Log node and group information using the logger.

Outputs the same information as __repr__ but using the logger, with properly formatted output for number of nodes and groups.

Examples

>>> nodes.logInfo()
# Logs:
# Number of nodes ................. : 100
# Number of groups ................ : 4
# Group table with names and counts

readNodalCoords(fin: TextIO) → None[source]

Read nodal coordinates from an open file stream.

Parses node definitions from a <Nodes> block until </Nodes> is encountered. Each line should contain: nodeID x [y [z]] with semicolon separators. Comments starting with // or # are ignored. Spatial dimension (rank) is inferred from the first valid node entry.

Parameters:: fin (TextIO) – Open file handle positioned at the start of the <Nodes> block.

Notes

Format: - Multiple nodes per line separated by semicolons - Format: nodeID x y [z]; - Whitespace is normalized before parsing - Comments (// or #) are skipped - rank is set from first node (2D or 3D)

readNodegroup(fin: TextIO, key: str) → None[source]

Read a node group from an open file stream.

Parses node IDs from a <NodeGroup> block until </NodeGroup> is encountered. Node IDs are whitespace-separated integers. All valid integers found are added to the specified group.

Parameters:

fin (TextIO) – Open file handle positioned at the start of a <NodeGroup> block.
key (str) – Group name label to assign these nodes to.

Notes

Format: - <NodeGroup name=”groupname”> - nodeID1 nodeID2 nodeID3 … - </NodeGroup>

getRank() → int[source]

Return the spatial dimension (rank) of the nodes.

Returns:: Spatial dimension (rank) of the nodes.
Return type:: int