May I know the meaning of this line?

[berttggg]

To my best understanding, self.env.agents is a list of names of all current agents, so if not self.env.agents will always return False?

https://github.com/Toni-SM/skrl/blob/7b090a1674b3ff1240a49385bd7fd757571f7145/skrl/trainers/torch/base.py#L311C24-L311C39

[Toni-SM]

Hi @berttggg

skrl multi-agent environment wrapper is based on PettingZoo Parallel API.
Then, there are 2 properties related to the available agents:

• possible_agents: A list of the names of all possible agents the environment could generate.. This cannot be changed through play or resetting.
• agents: A list of the names of all current agents. These may be changed as an environment progresses (i.e. agents can be added or removed).

The second one is used as condition to reset the environment as shown in the PettingZoo Parallel API Usage.

https://github.com/Farama-Foundation/PettingZoo/blob/f0c94c6f78a0d24a85d8e60f3685b076b4aa6510/docs/api/parallel.md?plain=1#L29

while env.agents:

Think of it as a game in which, as agents (players) lose, they are removed from the game (dropped from the list). Once all players lose (the list if empty), it is necessary to restart the game again :)