This little program convert all the indented code blocks in a markdown file to a fenced code blocks style.

indent2fence.py

"""
This little program convert all the indented code blocks
in a markdown file to a fenced code blocks style.
It adds python language highlight argument by default.

This program is argely inspired by the php gist made by tobice
https://gist.github.com/tobice/1beab9616bb48e56ac1f1eb48c11dd97

-p, --path : path to the file to convert
-t, --type : change the language highlight for the code blocks
             default is python

Returns:
    It is converted in the file itself.
"""

import re
from argparse import ArgumentParser

parser = ArgumentParser()
parser.add_argument(
    "-p",
    "--path",
    help='file path to convert',
    type=str)
parser.add_argument(
    "-t",
    "--type",
    help='language type for the code blocks',
    type=str,
    default="python")
args = parser.parse_args()


def isCode(line, indentedCode):
    """Check if the line is code by looking for indent at the beginning

    Arguments:
        line {string} -- line is a string of one line the markdown file being processed

    Returns:
        boolean -- Returns True or False
    """
    if indentedCode:
        return re.search("^        ", line)
    else:
        return re.search("^    ", line)


def removeIndent(line):
    """Remove the indentation of the line

    Arguments:
        line {string} -- line is a string of one line the markdown file being processed

    Returns:
        string -- Returns the line without indentation
    """
    return re.sub("^    ", "", line)


def isEmpty(line):
    """Check if the line is empty

    Arguments:
        line {string} -- line is a string of one line the markdown file being processed

    Returns:
        boolean -- Returns True or False
    """
    return line == "" or re.search("^[\r\n]$", line)


with open(args.path, 'r', encoding='utf8') as f:
    inCode = False
    indentedCode = False
    output = []

    for line in f:  # process each line in the markdown file one by one
        if inCode:  # things to do when an indented code part is detected
            if isEmpty(line):  # if an empty line is detected we just append it to the output array
                output.append(line)
            # if the line was not empty and is code, append it without the indent
            elif isCode(line, indentedCode):
                output.append(removeIndent(line))
            else:  # if the line is not empty, and not code
                # output.append("\n")  # append a new line
                # change the last line to be the end of the code block
                if indentedCode:
                    output[len(output)-1] = "    ```\n"
                else:
                    output[len(output)-1] = "```\n"

                output.append("\n")
                output.append(line)
                inCode = False
                indentedCode = False
        else:
            if isCode(line, indentedCode):  # first line of code block detected
                # append a fenced line with code type
                if re.search("^        ", line):
                    indentedCode = True
                    output.append("    ```" + args.type + "\n")
                else:
                    indentedCode = False
                    output.append("```" + args.type + "\n")
                output.append(removeIndent(line))
                inCode = True
            else:
                output.append(line)

with open(args.path, 'w') as f:
    f.write("".join(output))