featureTags.py

import AppKit
import CoreText

def fontWithFeatures(fontName, fontSize=10, features=None):
    font = AppKit.NSFont.fontWithName_size_(fontName, fontSize)
    if not features:
        return font
    descriptor = CoreText.CTFontDescriptorCreateCopyWithAttributes(font.fontDescriptor(), {CoreText.kCTFontFeatureSettingsAttribute: features})
    return AppKit.NSFont.fontWithDescriptor_size_(descriptor, fontSize)


fontName = font('/Users/frederik/Downloads/DrawBot Error/SourceSerifPro-Bold.otf')

s = FormattedString()
for fea in ["numr", "dnom", "sinf", "sups"]:

    aFont = fontWithFeatures(fontName, 100, features=[fea])

    attributes = {
        AppKit.NSForegroundColorAttributeName: AppKit.NSColor.redColor(),
        AppKit.NSFontAttributeName: aFont
    }

    txt = AppKit.NSAttributedString.alloc().initWithString_attributes_("123", attributes)
    s.getNSObject().appendAttributedString_(txt)
    
text(s, (10, 100))