Pajek read/write: store and read tabular data as attributes

[janezd]

Issue

Fixes #286. Fixes #275.

Description of changes

When saving, add data about nodes and edges. For nodes, this data is saved in the same format as in NetworkX, which is a hack of what's in Pajek. For edges, the format is the same, though unsupported by NetworkX (AFAIK).

When reading -- read the data save in this way.

The format is a mess: it allows (but doesn't require) node coordinates. Edges may have a numeric weight or a non-numeric label, but not both, to which we now add NetworkX-like key-value pairs, and so forth.

Tests for existing mess are lacking, and the new tests might not cover all possible combinations.

Includes

• Code changes
• Tests
• Documentation

[Copilot]

Pull request overview

This PR extends the Pajek (.net) import/export support to preserve tabular node/edge data as key–value attributes (in a NetworkX-like style) and updates the Save/Load widgets and tests to exercise the new behavior.

Changes:

• Enhance Pajek reader/writer to parse and emit node/edge attribute key–value pairs, producing Orange Table-backed node/edge data when present.
• Update Save Network widget UI to allow choosing node/edge label variables and optionally appending remaining attributes on save.
• Add/extend tests and test fixtures for quoted labels and attribute round-tripping.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
orangecontrib/network/widgets/OWNxSave.py	Adds UI/settings for node/edge label selection and optional attribute appending when saving.
orangecontrib/network/widgets/OWNxFile.py	Adjusts node data output behavior when the underlying network already stores nodes as a Table.
orangecontrib/network/network/tests/towns.net	Quotes a multi-word edge label to match new shlex parsing behavior.
orangecontrib/network/network/tests/towns-2.net	New fixture covering node + edge attributes and mixed edge value/attributes cases.
orangecontrib/network/network/tests/test_readwrite.py	Adds tests for reading/writing attributes and helper utilities.
orangecontrib/network/network/readwrite.py	Implements parsing/writing of vertex/edge attributes and table conversion helpers.
i18n/si/msgs.jaml	Adds translation keys for newly introduced UI strings and read/write formatting strings.

Comments suppressed due to low confidence (5)

orangecontrib/network/widgets/OWNxSave.py:112

• In set_network, the edge-label setup uses network.edges[0] without checking that network.edges is non-empty (Pajek files can contain vertices only), which can raise IndexError when a network has no edges.

        if isinstance(network.edges[0].edge_data, Table):
            self.controls.edge_variable.setEnabled(True)

orangecontrib/network/widgets/OWNxSave.py:115

• domain = network.edges.domain is invalid because network.edges is a list; this will raise AttributeError. The domain should come from the edge data table (e.g. network.edges[0].edge_data.domain).

            self.controls.edge_variable.setEnabled(True)
            domain = network.edges.domain
            self.edge_model.set_domain(domain)
            for attr in domain.metas:

orangecontrib/network/widgets/OWNxSave.py:121

• The hint restoration logic is broken: it does domain[self.edge_variable] (where self.edge_variable is a Variable, not a name) and then checks it against self.edge_model. This will either error or never match; it should look up domain[self.edge_variable_hint] (and also verify the variable is in self.edge_model).

            if self.edge_variable_hint in domain and \
                    (attr := domain[self.edge_variable]) in self.edge_model:
                self.edge_variable = attr

orangecontrib/network/widgets/OWNxSave.py:149

• dict_rows_from_table(..., self.label_variable) / (..., self.edge_variable) passes a Variable object into the exclude parameter, but dict_rows_from_table compares attr.name != exclude (string vs Variable), so the selected label column will not be excluded and will be duplicated in the saved attributes. Pass the variable name (or extend dict_rows_from_table to accept a Variable).

            if self.append_node_data and isinstance(data := net.nodes, Table):
                label_data = dict_rows_from_table(data, self.label_variable)
            else:
                label_data = None
            if self.append_edge_data and isinstance(data := net.edges[0].edge_data, Table):
                edge_data = dict_rows_from_table(data, self.edge_variable)
            else:

orangecontrib/network/widgets/OWNxSave.py:117

• Default label auto-detection only looks for meta variables named node_label / edge_label, but this PR’s Pajek reader/writer uses node label / edge label (with spaces). This prevents the widget from auto-selecting the correct label variable for Pajek-loaded networks; consider accepting both naming variants.

            for attr in domain.metas:
                if attr.name == "node_label":
                    self.label_variable = attr
                    break
            if self.label_variable_hint in domain and \
                    (attr := domain[self.label_variable_hint]) in self.label_model:
                self.label_variable = domain[self.label_variable_hint]
        else:
            self.label_model.set_domain(None)
            self.label_variable = None
            self.controls.label_variable.setEnabled(False)

        if isinstance(network.edges[0].edge_data, Table):
            self.controls.edge_variable.setEnabled(True)
            domain = network.edges.domain
            self.edge_model.set_domain(domain)
            for attr in domain.metas:
                if attr.name == "edge_label":
                    self.edge_variable = attr

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