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Agent-Based Models with Python: An Introduction to Mesa

Geoff Evamy Hill
16 Oct 2024 11:21am UTC
1
in Agent-Based Models with Python: An Introduction to Mesa

Hi there,
I am getting this error when I run the code from step 7.
"""
self.grid.place_agent(trader, (x,y))
:83: UserWarning: Agent 4139 is being placed with
place_agent() despite already having the position (30, 30). In most
cases, you'd want to clear the current position with remove_agent()
before placing the agent again.
"""

It seems to happen with the code from the github as well. Any ideas?

Zhaohan
28 Nov 2024 12:41am UTC
in Agent-Based Models with Python: An Introduction to Mesa

Hi Geoff，
place_agent method checks whether the agent already has a position before placing it. You could simply solve this issue by setting pos = None when creating a new agent. Here is the source code.
@warn_if_agent_has_position_already
def place_agent(self, agent: Agent, pos: Coordinate) -> None:
"""Place the agent at the specified location, and set its pos variable."""
x, y = pos
if agent.pos is None or agent not in self._grid[x][y]:
self._grid[x][y].append(agent)
agent.pos = pos
if self._empties_built:
self._empties.discard(pos)
self._empty_mask[agent.pos] = True

Tom Youngman
16 Oct 2024 3:16pm UTC
5
in Agent-Based Models with Python: An Introduction to Mesa

I'm running the code as shown in session 5 but getting the follow error - any ideas?

---------------------------------------------------------------------------

ValueError Traceback (most recent call last)

in ()
----> 1 model = SugarscapeG1mt()

in __init__(self, width, height)
19
20 agent_id = 0
---> 21 for (x,y) in self.grid.coord_iter():
22 max_sugar = sugar_distribution[x,y]
23 if max_sugar > 0:

ValueError: too many values to unpack (expected 2)

Tom Youngman
16 Oct 2024 3:44pm UTC
in Agent-Based Models with Python: An Introduction to Mesa

I've not figured out the error:
for _,(x,y) in self.grid.coord_iter():

needs the brackets around (x,y) removed to become:
for _,x,y in self.grid.coord_iter():

I have forked the session 5 on GitHub and suggested the change

Eka Putri Difayanti
10 Nov 2024 10:37pm UTC
in Agent-Based Models with Python: An Introduction to Mesa

I have the same problem. Did you find a solution?

Kai Greenlees
26 Nov 2024 12:18pm UTC
in Agent-Based Models with Python: An Introduction to Mesa

I've had the same problem as well, did anyone come across a solution?

Tom Youngman
26 Nov 2024 12:21pm UTC
in Agent-Based Models with Python: An Introduction to Mesa

Did this fix not work?
for _,(x,y) in self.grid.coord_iter():

needs the brackets around (x,y) removed to become:
for _,x,y in self.grid.coord_iter():

Kai Greenlees
26 Nov 2024 12:56pm UTC
in Agent-Based Models with Python: An Introduction to Mesa

Hi Tom, actually I am struggling with another issue when I try to run the last step in the fifth session I get this error about the number of arguments being incorrect with the __init__() function in the Sugar agent parameters, but the code I've used is a direct copy of the Session 5 code provided. Any thoughts on how to troubleshoot would be greatly appreciated. I am new to Python & ABM so the syntax is still new to me

Error message:
TypeError Traceback (most recent call last)
in ()
----> 1 model = SugarscapeG1mt()

2 frames
/usr/local/lib/python3.10/dist-packages/mesa/agent.py in __init__(self, model, *args, **kwargs)
62
63 """
---> 64 super().__init__(*args, **kwargs)
65
66 self.model: Model = model

TypeError: object.__init__() takes exactly one argument (the instance to initialize)

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