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OSX: Fatal error: Duplicate keys

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Fatal error: Duplicate keys of type 'DisplayList' were found in a Dictionary. This usually means either that the type violates Hashable's requirements, or that members of such a dictionary were mutated after insertion.

this in a WXPython 4.02 app (wx not upgraded recently) and wx doesn't have a 'DisplayList' class and neither does my app.

started happening shortly after upgrading Wing Pro, but I also upgraded the OS too

this isn't an exception. it gets written to the Debug/IO window and debugging stops OSX Sonoma 14.3.1 (23D60), WING Pro (rev 363662fe5c92)

seems like this is a swift related thing so may not be in wing see:…

jbpence's avatar
asked 2024-02-19 06:25:00 -0500
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doesn't happen other than when wing IDE is debugging.

jbpence's avatar jbpence (2024-02-19 06:26:24 -0500) edit
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1 Answer


The debugger is probably changing how the program is executed. This can happen, particularly in threaded code. You may want to attach a Swift debugger to it and hopefully see what is inserting the duplicate key (I assume this is possible, but haven't worked with Swift so could be wrong). We'd probably need a reproducible test case in order to look into it ourselves.

Wingware Support's avatar
Wingware Support
answered 2024-02-19 06:50:56 -0500
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thanks looking into it

jbpence's avatar jbpence (2024-02-20 14:48:13 -0500) edit
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