Description

Fixes RuntimeWarning: More than 20 figures have been opened by replacing plt.subplots() with direct Figure() instantiation throughout the visualization codebase.

Problem

The pyplot interface (plt.subplots()) maintains a global registry of all figures, preventing garbage collection and causing memory accumulation. When tests run in sequence, the accumulated figure count exceeds matplotlib's default warning threshold of 20 figures.

Solution

Replace all plt.subplots() calls with direct Figure() instantiation:

# Before
fig, ax = plt.subplots(constrained_layout=True)

# After  
from matplotlib.figure import Figure
fig = Figure(constrained_layout=True)
ax = fig.add_subplot()

Files Changed

• mesa/visualization/backends/matplotlib_backend.py - Updated initialize_canvas() (1 instance)
• tests/test_components_matplotlib.py - Updated all test functions (15 instances)