Sometimes, you need a small job done, and you can write a small Python program, and it does just what you need, and it pleases you.

I have some Markdown files to convert to ReStructured Text. Pandoc does a really good job. But it chooses a different order for heading punctuation than our house style, and I didn’t see a way to control it.

But it was easy to write a small thing to do the small thing:

import re
import sys

# The order we want our heading rules.
GOOD_RULES = '#*=-.~'

# A rule is any line of all the same non-word character, 3 or more.
RULE_RX = r"^([^\w\d])\1\1+$"

def rerule_file(f):
    rules = {}
    for line in f:
        line = line.rstrip()
        rule_m = re.search(RULE_RX, line)
        if rule_m:
            if line[0] not in rules:
                rules[line[0]] = GOOD_RULES[len(rules)]
            line = rules[line[0]] * len(line)
        print(line)

rerule_file(sys.stdin)

If you aren’t conversant in .rst: there’s no fixed order to which punctuation means which level heading. The first rule encountered is heading 1, the next style found is heading 2, and so on.

There might be other ways to do this, but this makes me happy.