Add a HTML comment on every Django/Jinja2 {% block %} template tag to find out from which file a rendered output is coming from

add_block_comment.py

#!/usr/bin/python3.5
import glob
import re


def replace_generator(fn):
    def replace(match):
        return '{}\n<!-- file: {} block: {} -->\n'.format(match.group(0), fn, match.group(2))
    return replace


for filename in glob.iglob('./**/*.html', recursive=True):
    try:
        f = open(filename)
        data = f.read()
        f.close()

        data = re.sub('({%-? block ([a-zA-Z0-9_\-]+) -?%})', replace_generator(filename), data)

        data = '<!-- {} -->\n'.format(filename) + data
        f = open(filename, 'w')
        f.write(data)
        f.close()
    except:
        import traceback
        traceback.print_exc()