Open a project with masters that have both italicAngle=0 and italicAngle!=0, then run this in the macro window:
import GlyphsApp
for master in Glyphs.font.masters:
print(master.name, master.italicAngle)
The expected outcome is for the correct italic angles to be printed, but I see 0.0 for most (!?) masters, until I explicitly view them in the GUI (ie tap each of the master buttons in the app’s toolbar to switch to it.)
Here’s a screen recording:
Glyphs 3.1 (3133) with Python version set to “3.9.1 (Glyphs)” in settings.
The odd display of the float value can happen. This is how floats work. So for displaying it, you always need to check the significant digits and display accordingly. Internally it is a double with the “correct” value.