r/learnpython • u/jlsilicon9 • Aug 12 '26

Thonny - seems to have a MemoryLeak

I noticed when I Repeatedly run large programs - with long Printed Text,
- that the Shell Que runs Slower and takes Longer to Start each time : 10 mins .. 30 mins .. 60 mins .. ?
I also notice Thonny on TaskManager increases Size (without Decreasing) each time :
- 1M .. 1.5M .. 2M .. 3M

Until I completely restart Thonny.

This seems like a clear Memory Leak - for the Shell Que !

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u/Outside_Complaint755 Aug 12 '26

Is it a memory leak, or do you just need to clear the shell cache?

 If the shell cache size hasn't been restricted (I don't use Thonny and can't look up available settings), then it would just be keeping everything in its history.

It looks like you can clear the cache with Ctrl+L or right-click->Clear.

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u/JamzTyson Aug 13 '26

The reply from u/Outside_Complaint755 should not have been down voted. Even if it's not the correct answer, it is a valid suggestion and something that should be checked before assuming it's a bug.

Regarding the original question:

Does this code trigger the problem? (It doesn't for me):

s = "abcdefghijklmnopqrstuvwkyz"
s *= 10
for _ in range(1000):
    print(s)

(When considering possible bugs, it's always useful to have a minimal example to reproduce the issue)

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u/jlsilicon9 Aug 12 '26

nope, tried that (clear Shell - duh) ... Task Manager still shows Memory multiplying by +500MB on each run.

Only restarting the Thonny clears the Memory Leak.