widths.py

# type your Python code here and press cmd+Return to run.
reference = "n"
glyph = Glyphs.font.glyphs[reference].layers[0]

referenceWidth = glyph.width - glyph.LSB - glyph.RSB
print "Reference:", reference, referenceWidth

for char in ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"]:
	curGlyph = Glyphs.font.glyphs[char].layers[0]
	width = curGlyph.width - curGlyph.LSB - curGlyph.RSB
	print char, width / referenceWidth * 100, "%"