v2.4.0

Highlights

Mesa 2.4.0 brings several key improvements from the upcoming 3.0 series, while maintaining compatibility with existing Mesa 2.x models.

The DataCollector now supports collecting data from specific Agent subclasses using the new agenttype_reporters parameter (#2300). This allows collecting different metrics for different agent types. For example:

self.datacollector = DataCollector(
    agenttype_reporters={
        Wolf: {"sheep_eaten": "sheep_eaten"},
        Sheep: {"wool": "wool_amount"}
    }
)

The AgentSet class, which underpins model.agents, has received major enhancements:

• A new groupby() method to split agents into groups (#2220)
• An agg() method to quickly compute aggregate values (#2266)
• A faster shuffle_do() method for more efficient random agent activation (#2283)
• The select() method now allows choosing a fraction of agents (#2253)
• The do() method can now take any callable function, not just string method names (#2219)

Other notable improvements include:

• The Model class now exposes an agents_by_type property for easier access to agents of specific types (#2267)
• Performance enhancements for Model.agents (#2251)
• The AgentSet.get() method now handles missing values with optional default value (#2279)

This release also fixes a bug in the Grid's move_agent_to_one_of method with selection="closest", which previously selected locations deterministically instead of randomly (#2118).

Finally, we've made significant documentation improvements, including the addition of a new Migration guide to help users transition to future Mesa versions (#2257).

What's Changed

🎉 New features added

• Add AgentSet.groupby by @quaquel in #2220
• AgentSet: Add agg method by @EwoutH in #2266
• GroupBy: Add count and agg methods by @EwoutH in #2290
• datacollector: Allow collecting data from Agent (sub)classes by @EwoutH in #2300
• Add optimized shuffle_do() method to AgentSet by @EwoutH in #2283

🛠 Enhancements made

• Allow AgentSet.do() to take Callable function by @quaquel in #2219
• Split AgentSet into map and do to separate return types by @quaquel in #2237
• Performance enhancements for Model.agents by @quaquel in #2251
• AgentSet: Allow selecting a fraction of agents in the AgentSet by @EwoutH in #2253
• Model: Replace get_agents_of_type method with agents_by_type property by @EwoutH in #2267
• Add default values and missing value handling to agentset.get by @quaquel in #2279

🐛 Bugs fixed

• Jupyter_viz: Allow measures to be None by @EwoutH in #2163
• Fix deterministic behavior in move_agent_to_one_of with selection="closest" by @OrenBochman in #2118

📜 Documentation improvements

• Contribution: Add "I have no idea where to start" section by @EwoutH in #2258
• Write initial Mesa Migration guide by @EwoutH in #2257
• Docs: Fix broken relative links by removing .html suffix by @EwoutH in #2274
• Readthedocs: Don't let notebook failures pass silently by @EwoutH in #2276
• update migration guide to describe solaraviz updates by @Corvince in #2297
• Migration Guide: Add Model initialization requirement and automatic Agent.unique_id assignment by @EwoutH in #2302

🔧 Maintenance

• make typing behavior of AgentSet.get explicit by @quaquel in #2293

Full Changelog: v2.3.4...v2.4.0