Prusa Slicer post-processing script for z speed

import os
import re
import sys
import shutil

src = sys.argv[1]
src_file_parts = os.path.splitext(src)

if src_file_parts[1] == '.gcode':
    src_old = src
    src = src_file_parts[0] + '.g'
    os.rename(src_old, src)

# Uncomment if you would like to create a backup file before processing
# bkp = src+'.bkp'
# shutil.copyfile(src, bkp)

with open(src, 'r') as src_file:
    content = src_file.read()
    result = re.sub('G1 Z([\d\.]*) F4800.000', r'G1 Z\1 F420', content, flags = re.M)
with open(src, 'w') as res_file:
    res_file.write(result)