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name: wrappers-and-utilities description: "Use PettingZoo conversion wrappers, utility wrappers, AgentSelector, reward/observation helpers, and wrapper troubleshooting guidance." disable-model-invocation: true metadata: disco-role: operating license: NOASSERTION

Wrappers And Utilities

Use this sub-skill when an agent needs to convert between PettingZoo AEC and Parallel APIs, compose utility wrappers, diagnose wrapper errors, use AgentSelector, compute random-policy reward baselines, save image observations, or capture text rendering.

Read Or Run

• Read references/wrappers-and-conversions.md when you need aec_to_parallel, parallel_to_aec, turn_based_aec_to_parallel, wrapper ordering, AEC-vs-Parallel limitations, base wrappers, or multi-episode wrappers.
• Read references/utilities.md when you need AgentSelector, average_total_reward, save_observation, CaptureStdoutWrapper, capture_stdout, or EnvLogger guidance.
• Read references/troubleshooting.md when conversion assertions, order-enforcing errors, illegal-action termination, out-of-bounds actions, render/reset problems, or observation-saving failures occur.
• Run scripts/wrapper_conversion_smoke.py when you need a bounded, dependency-light check that parallel_to_aec and valid aec_to_parallel conversion semantics work in the installed PettingZoo package.

Route Elsewhere

• For ordinary AEC or Parallel rollout loops, action-mask sampling in policies, rendering choices, and step(None) control flow, use ../use-environments/SKILL.md.
• For implementing new environment internals, raw_env() factories, _was_dead_step, _clear_rewards, or custom AgentSelector turn logic, use ../custom-environments/SKILL.md.
• For compliance tests such as api_test, parallel_api_test, seed tests, render tests, or native wrapper test selection, use ../testing-and-validation/SKILL.md.

Default Stance

Treat PettingZoo's utility wrappers as mostly AEC-oriented. If a user starts from a Parallel environment, convert to AEC when needed, apply AEC wrappers there, then convert back only when the environment satisfies the parallel-conversion assumptions.