GIT rename bunch of files using python

rename.py

#!/usr/bin/env python3
import subprocess
import time
from os import walk, path, chdir
import re
regex = re.compile(r'([0-9a-f]+)_(\w+)\.py')
date_re = re.compile(r'(\d+)-(\d+)-(\d+) (\d+):(\d+)')

chdir('/Users/h4/Projects/Arrival/components-catalogue/alembic/versions')
for root, dirs, files in walk('/Users/h4/Projects/Arrival/components-catalogue/alembic/versions'):
    for fname in files:
        if fname.endswith('.py'):
            if regex.match(fname):
                full_path = path.join(root, fname)
                with open(full_path) as fp:
                    for i, line in enumerate(fp):
                        if i == 4:
                            prefix = ''.join(date_re.search(line).groups())
                        if i > 5:
                            break
                newname = prefix + '_' + regex.sub(r'\2_\1.py', fname)
                subprocess.run(["git", "mv", fname, newname])