preprocess_code.py

#!/usr/bin/env python3

# This script consumes Markdown preformatted code blocks delimited by ``` and
# replaces them by inline HTML with line numbers. This would be a good way to
# add syntax hilighting later,

import sys
import pygments
import pygments.formatters
#  from pygments.lexers import PythonLexer
import pygments.lexers

fmt = pygments.formatters.HtmlFormatter(linenos="table", noclasses=True)

# When state is true, we are inside of a codeblock
state = False
code = ""
language = ""
for line in sys.stdin:
    if line.strip()[0:3] == '```':
        # state transition edge

        state = not state

        if not state:
            # state transition from in code block to not in code block
            lexer = None
            try:
                lexer = pygments.lexers.get_lexer_by_name(language)
            except Exception:
                # the user-provided language was unknown, guess instead
                lexer = pygments.lexers.guess_lexer(code)
            h = pygments.highlight(code, lexer, fmt)
            sys.stdout.write(h)

            language = ""
            code = ""

        else:
            # state transition from not code block to code block
            language = line[3:].strip()

    elif state:
        # we are not in a state transition, and we are reading a codeblock
        code += line
    else:
        # pass lines through unmodified
        sys.stdout.write(line)