[Solved] You wrote this code but get an error: RuntimeError: main thread is not in main loop. What is the likely cause? import matplotlib.pyplot as plt matplotlib.use('Agg') plt.plot([1,2,3],[4,5,6]) plt.... | Matplotlib

Matplotlib - Performance and Large Data

You wrote this code but get an error: RuntimeError: main thread is not in main loop. What is the likely cause?

import matplotlib.pyplot as plt
matplotlib.use('Agg')
plt.plot([1,2,3],[4,5,6])
plt.savefig('out.png')

ANot calling plt.close() after saving.

BSetting backend after importing pyplot.

CUsing plt.savefig instead of plt.show.

DPlotting with empty data lists.

Step-by-Step Solution

Solution:

Step 1: Check import and backend order
The error occurs because backend is set after importing pyplot, which is too late.
Step 2: Correct order to fix error
Set backend with matplotlib.use('Agg') before importing pyplot to avoid this error.
Final Answer:
Setting backend after importing pyplot. -> Option B
Quick Check:
Backend must be set before pyplot import [OK]

Quick Trick: Set backend before pyplot import to fix runtime errors [OK]

Common Mistakes:

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You wrote this code but get an error: RuntimeError: main thread is not in main loop. What is the likely cause?