bolder.py

#!/usr/bin/env python
# Script shamelessly stolen from: https://github.com/shytikov/pragmasevka

import sys
import fontforge

if len(sys.argv) < 2:
    print("Please provide path prefix of the font to update!")
    exit()

prefix = sys.argv[1]

glyphs = [
    "exclam", "ampersand", "parenleft", "parenright", "asterisk", "plus",
    "comma", "hyphen", "period", "slash", "colon", "semicolon", "less",
    "equal", "greater", "question", "bracketleft", "backslash", "bracketright",
    "asciicircum", "braceleft", "bar", "braceright", "asciitilde",
]

pairs = [
    ['regular', 'semibold'],
    ['italic', 'semibolditalic'],
    ['bold', 'black'],
    ['bolditalic', 'blackitalic'],
]

for [recipient, donor] in pairs:
    font = f"{prefix}-{recipient}.ttf"

    target = fontforge.open(font)
    # Finding all punctuation
    target.selection.select(*glyphs)
    # and deleting it to make space
    for i in target.selection.byGlyphs:
        target.removeGlyph(i)

    source = fontforge.open(f"{prefix}-{donor}.ttf")
    source.selection.select(*glyphs)
    source.copy()
    target.paste()

    target.generate(font)