Did putting GSPen in the Scripts folder fix the problem with LS Cadenculator? That is what is was supposed to fix.
::edit:: That fix I wrote about was from a year ago. I just tried to test Cadenculator and find that I once again have the same problem, so now it doesn’t fix anything.
Thank you @George_Thomas! No unfortunately it did not help…yeah. well but besides LS Cadenculator other plugins from Plugin manager do not work as well at all 
Frankly, there must be something else wrong with your system setup that is interfering with Python execution. Remote diagnosing seems impossible. Can you ask someone knowledgeable about Python for help who can have physical access to your Mac?
Yes. I asked @RafalBuchner but he also did not know why glyphs cannot find installed python libraries.
~/Library/Application Support/Glyphs/ and all its subfolders.Which macOS are you running?
The only other thing I can imagine at this point is that there is something more profoundly broken on your system, which is impossible to remote-diagnose. Consider using a different machine or doing a clean install.
This is what Install Modules does now.
How do you tell? Which plug-in are you test-installing?
I just looked back at my support emails from the LS Cadencer/Cadenculator developer, and there is one dependency you may not have installed: the DrawBot plugin, which can be installed through the Plugin Manager in Glyphs.
I had DrawBot installed when I first got LS Cadencer/Cadenculator but had removed it since I never used it. Restoring it fixed the issue with LS Cadenculator so may fix other issues as well.
Any plugin I try to Install don’t work, I tried with stemTickness in an empty version of glyphs and I get this error message:
Traceback (most recent call last):
File “/Users/nieuw/Library/Application Support/Glyphs/Repositories/StemThickness/StemThickness.glyphsReporter/Contents/Resources/boot.py”, line 47, in
_run(‘StemThickness.py’)
File “/Users/nieuw/Library/Application Support/Glyphs/Repositories/StemThickness/StemThickness.glyphsReporter/Contents/Resources/boot.py”, line 45, in _run
execfile(path, globals(), globals())
File “/Users/nieuw/Library/Application Support/Glyphs/Repositories/StemThickness/StemThickness.glyphsReporter/Contents/Resources/StemThickness.py”, line 14, in
from GlyphsApp.plugins import *
File “GlyphsApp/init.py”, line 978, in
objc.BadPrototypeError: Objective-C expects 1 arguments, Python argument has 2 arguments for <unbound selector callback of callbackHelperClass at 0x127639988>
Im using the last OSX version Sierra 10.12.6
Are you sure you are running Python 2.7? Can you please paste this in your macro window and press Run:
import sys
print sys.version
…and tell me what the result is?
I get this error
2.7.10 (default, Feb 7 2017, 00:08:15)
[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.34)]
Edited for clarity --mekkablue
The import/print lines only produced those two lines. In my case it is:
2.7.10 (default, Jul 15 2017, 17:16:57)
[GCC 4.2.1 Compatible Apple LLVM 9.0.0 (clang-900.0.31)]
Did you ever install Xcode or developer tools?
I guess I have to switch to robofont
Would installing Xcode/Developer Tools cause problems with Glyphs plug-ins?
I installed Xcode but just few days ago, I have problem with glyphs since 16 of November
Can you tell me what happens in Console.app when you start the app, or try to run a Python script?
If the same happens in a different user as well, as you suggested further above, I am afraid the problem lies deeper and you will have to reinstall your system.
We could solve the problem. The python environment is not right but we could find a way to get it to work.
Yeaaah! Georg Fixed it! Thank you so much again!
Hi Georg and Edward, because from time to time some of my Antwerp students encounter the same problem with the LS Cadencer and Cadenculator in Glyphs, I was wondering whether you could stepwise explain how you solved it. Thanks in advance!
Which problem exactly? Can you point me to an URL for the Python libraries you are trying to access?
Hi Rainer, the problem with which this thread was started by Edward: ‘Hello, I just bought and installed Glyphs today but there is a problem with plugins. I tried to install @RafalBuchner stemthickness as well as LScadencer and glyphs doesn’t see both of them.’ Obviously Georg came up with a smart solution after a long discussion: ‘Yeaaah! Georg Fixed it!’