sgtl.graph.from_edgelist#

sgtl.graph.from_edgelist(filename, directed=False, num_vertices=None, **kwargs) → Graph#

Construct an sgtl.Graph object from an edgelist file.

The edgelist file represents a graph by specifying each edge in the graph on a separate line in the file. Each line looks like:

id1 id2 <weight>

where id1 and id2 are the vertex indices of the given edge, and an optional weight is given as a floating point number. If any edge has a specified weight, then you must specify the weight for every edge. That is, every line in the edgelist must contain the same number of elements (either 2 or 3). The file may also contain comment lines.

By default, the elements on a given line are assumed to be separated by spaces, and comments should begin with a ‘#’ character. These defaults can be changed by passing additional key-word arguments which will be passed to pandas.read_csv.

Parameters:

  • filename – The edgelist filename.

  • directed – Whether the graph is directerd.

  • num_vertices – The number of vertices in the graph, if this is known in advance. Specifying this value will speed up the method.

  • kwargs – Key-word arguments to pass to the pandas.read_csv method which will be used to read in the file. This can be used to set a delimiter other than the space character, or to change the comment character.

Returns:

the constructed sgtl.Graph object

Raises:

TypeError – If the edgelist file cannot be parsed due to incorrect types.

Example:

An example edgelist file is as follows:

# This is a comment line
0 1 0.5
1 2 1
2 0 0.5

The above file gives a weighted triangle graph.