The software Pajek has its own requirement for describing a graph/network. However, the edgelist and adjacency matrix may be the most intuitive way of representing a network/graph.
Moreover, it's well known that a network contains not only connection/topology information, but also attributes of components such as the features of a node or classes of a relationship.
The features/attributes of network components can be intuitively stored or organized by tables of database.
Thus, most of the information of a network can be represented by an edgelist/adjacency matrix and several tables.
In order to process/visualize a network with the tool Pajek, people need to prepare the network data as the form that can be processed by Pajek.
I looked into the wiki of Pajek and find how to convert an edgelist into .net file for Pajek. Furthermore, the tables that stores attribute of vertices can also be converted into .clu file by this code.
As the Pajek required, a network can be stored into several kinds of files such as: .netfile, .clufile, .vecfile, .perfile, etc.
Below is a .netfile example, details are described in link (page 8, Figure 3)
*Vertices 4
1 "Ada" 0.1646 0.2144 0.5000
2 "Cora" 0.0481 0.3869 0.5000
3 "Louise" 0.3472 0.1913 0.5000
4 "Jean" 0.1063 0.5935 0.5000
< index > < Lable > < coordinates >
*Arcs :1 "Dining-table partner choice"
1 3 2
1 2 1
2 1 1
2 4 2
< start > < end > < type of connection >
*Edges :2 "Cooperation"
1 2 1 l "Math 2a"
2 4 1 l "Math 2a"
1 4 1 l "Math 2a"
2 3 1 l "Geo 1"
Note: the <...> is comment but not the content of the .net file.
The .net file above defines the connections by Arcs(directed), and Edges(undirected) and their types(the number after the colon, : ) and Lables("Dining-table par...")
Check the comments in the source code file edgelist2pajek.py
Using networkx can be a quite direct way to handle these tasks. ref: https://networkx.github.io/documentation/networkx-2.3/reference/readwrite/pajek.html