PyQt5 and Big Sur

Jeremy Katz jkatz at
Sun Nov 15 22:35:07 GMT 2020

On 15/Nov/20 04:50, Eric Larson wrote:
> I recently updated to Big Sur (11.0.1). I have Qt5Agg set as my
> matplotlib backend. Opening a matploltlibĀ figure in interactive mode now
> causes the interpreter to hang on 5.12 and 5.15.1. Even running a hello
> world <> example
> causes the interpreter to hang.
> I tried the same matplotlib code with pyside2, and there at least the
> interpreter would not hang. For both PyQt5 and pyside2, however, no
> window actually showed up, even though an icon did appear. So it seems
> at least some of this is probably a problem at the level of Qt rather
> than PyQt5.

I had an apparent application hang with PyQt and Qt 5.15.0, and an
application bundle created with PyInstaller. Dtruss revealed that the
application was executing, but very slowly. IIRC, the main window went
from displaying in ~5 seconds with macOS Catalina to 4 minutes with Big Sur.

Running the application once with "open -F" seemed to resolve the issue

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