https://qiita.com/shiracamus/items/6772be86ef1f863bcd2e

autopep8md.py

import os
import sys
import subprocess
import tempfile


def autopep8(code):
    with tempfile.NamedTemporaryFile('w', delete=False) as f:
        f.write(code)
        code_file_name = f.name
    subprocess.run(['autopep8', '-i', code_file_name])
    with open(code_file_name) as f:
        code = f.read()
    os.unlink(code_file_name)
    return code


def autopep8markdown(lines):
    in_code_block = False
    for line in lines:
        if not in_code_block:
            yield line
            if '```py' in line:
                in_code_block = True
                code = ''
        else:
            if '```' not in line:
                code += line
            else:
                yield autopep8(code)
                yield line
                in_code_block = False


def input_lines():
    if len(sys.argv) == 1:
        return sys.stdin.readlines()
    else:
        return open(sys.argv[1]).readlines()


def output_lines(lines):
    for line in lines:
        print(line, end='')


def main():
    output_lines(autopep8markdown(input_lines()))


if __name__ == '__main__':
    main()